These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: Girls' Generation
Broken Base: A very mild version, when Tiffany announced in mid 2013 that there would be more singles by TaeTiSeo (instead of another subunit, as had been previously thought and hoped for), some Sones... were unhappy.
Well, Yuri and Hyoyeon have since announced that there will be new subunits, so things seem to have been smoothed over for now.
Creator's Pet - A fairly mild example in Yoona. Some people resent that she is constantly at the centre of every performance and was the sole member to be featured on the Run Devil Run CD cover (despite not being the strongest singer/dancer in the group) and generally "over-exposed" (to the detriment of the other members).
For example: in their promos/MV for the The Boys, Yoona was featured the most out of all the other members, and has been labelled as a "lead rapper", despite having the same amount of "rap" lines as Sooyoung, Hyoyeon, Tiffany and Yuri.
Note that Yoona's now listed as a main rapper along with Yuri - meaning that they are the "best" rappers in SNSD, while she rapped the second least on "I Got A Boy", while Sooyoung is listed as a lead rapper (along with Hyoyeon, lead meaning "second-best rapper"), while her appearance in the song was almost nothing but rapping!
There was actually a study done wherein it was discovered that the "Big Four" (Yoona, Jessica, Tiffany and Taeyeon) had a substantial amount more of lines/screentime than members like Sooyoung, Hyoyeon and Yuri (Seohyun and Sunny fell in the middle). One telling moment was when Jessica was revealed to have had three minutes and thirty seconds more screentime than Hyoyeon - practically the length of "Gee"! It doesn't seem like much at first, but when you think about it, you realize just how unfair it really is.
People are also starting to notice that Jessica's screentime/lines have suddenly shot up as well, despite her voice/personality◊ being very divisive in the fanbase. She's also drawing heat for seemingly not caring about her performances/dances◊ anymore◊ (a popular internet meme is to show gifs of SNSD dancing... and Jessica's will◊ alwaysbe◊ wrong◊).
To clarify - Jessica's nickname is "The Ice Princess/Lazy Princess", whose attitude◊ of being "cold, mean and aloof" and known tendency to be lazy◊ and "half-ass" her singing/dancing◊ is considered cute/adorable by some... and irritating/unprofessional by others.
And now people are saying that Jessica's parts are dropping in amount and difficulty, while Tiffany (who arguably doesn't have as stable a voice as say, Seohyun or Sunny) has been acquiring more and more lines and ad-libs (see "I Got A Boy" for a good example - especially the bridge, where it's just her and Taeyeon, while the others are basically indistinguishable in the background - see 3:38-3:50 here).
After the announcement of TaeTiSeo (the first subunit consisting of Taeyeon, Tiffany and Seohyun) some Sones started... behaving badly. Some claimed that SNSD was nothing without all nine members, and refused to support TaeTiSeo. Others went to the opposite of the spectrum, claiming that TaeTiSeo were the important members of the group, and that they were the only ones who should be supported (which might not seem too bad, except both Yoona and Yuri had dramas and Hyoyeon was being featured on Dancing with the Stars: Korean Version, so they were basically being ignored in favour of TaeTiSeo).
Things came to a head when someone message on a forum during Hyoyeon's run on Dancing with the Stars calling out people who pretended to be a fan of all nine members, but clearly neglected Hyoyeon. They mentioned that Tiffany had showed up in costume to support Hyoyeon, which meant she literally had had to run from the music show where she was performing to watch Hyoyeon, and go back. The only reason this would have happened is because Hyoyeon felt bad about not having anyone there to support her (while Taeyeon, Tiffany and Seohyun had loads of fans to support them).
Another in-fandom example is Yoona. Go ahead, mention she doesn't contribute anything to the group and that Yuri/Sooyoung is/are better actress(es). We'll be at yourfuneral.
Alternatively - is Jessica a gorgeous Ice Princess whose laziness is cute, or is she an annoying lazy brat who needs to stop being so unprofessional?
Hate Dumb: On the opposite side, we have STAND (Strong Til All Nine Disappear/Strong Til All Nine Disband/Strong Til All Nine Die). The less said about them, the better.
Fandom Rivalry - Most notably with ELFs, Super Junior's fandom. Which is pretty ironic, as both groups are from the same company and support each other very much.
Also between 2NE1 fans (Blackjacks) and Sones. Arguments mostly about the looks of the members of each group, and which group is more "talented". Just look at any of the comments in each of their music videos - it's enough to make you want to smack them all upside the head.
Then there was the whole CARTEL incident, a.k.a Black Ocean 2008. Cassies (DBSK fans), EL Fs (SJ fans) and Triple S (SS 501 fans) turned off their lightsticks at a concert for SNSD and... behaved badly. Suffice it to say that nobody was innocent - Sones apparently had a couple issues themselves - and that is all that we will say about that!
Tiffany's voice is so husky she sounds like she has a sore throat all the time.
Jessica doesn't do anything but sleep (except when cucumbers are around).
All Sooyoung does is eat and tease Taeyeon & Sunny for being short.
All Hyoyeon does is dance.
Harsher in Hindsight - During a segment of Star Golden Bell, one of the MCs had to guess whose mother was the woman who they had invited. One of the options was Tiffany. In fact, as soon as she appeared, the MC started to think that it had to be Tiffany's, since they really looked alike. All of this happened, of course, before it was revealed that Tiffany's mother passed away before her debut.
AnchoredShip / ShipSinking: TaengSic (Taeyeon x Jessica). No one knows what happened between them or why their interactions just completely stopped. WMG from fans range from them getting into a fight to Tiffany stealing Taeyeon away. Has also sort of become a fandom inside joke.
FanPreferredCouple: YMMV but TaeNy (Taeyeon x Tiffany). Just try searching up SNSD fanfiction; chances are, at least half of them is Tae Ny. Even their own agency seems to know how popular it is and makes use of it (Lost in Love duet anyone?).
The pairings are divided as follows: Royal (TaeNy, YulSic, YoonHyun, SooSun), Ace (JeTi, HyoYoung, SunYeon), Deuce/Full House (YulTi, YoonSic) and Dice (all other pairings).
Periphery Demographic - SNSD was originally marketed towards young men. However, they have lots of fans outside that demographic, e.g. ahjussi and samchon (middle aged men and uncles, respectively)... and girls.
Signature Song: Gee. The song has even managed to become something of a Memetic Mutation within the StarCraft community due to the line "Gee gee gee gee, baby baby baby" resembling "GG"; short for good game, typed near or at the end of a match.
Not to mention G-Dragon of Big Bang mentioned it in his song "Leaders": "My name is G-G-G baby baby baby GD GD baby baby."
Aram of G.I. (Global Icon) had a part in their song that went "G - G - G - G.I.".
Squick: It was recently revealed that a 46-year-old California man named Thomas Blevins had been pretending to be a video director for SM. What made this guy go leaps and bounds beyond your normal creep is he not only started a rumour about an English album that Taeyeon herself had to shut down, he also made a fake casting call for young girls and women to come out and dance for an alleged music video in LA. He also had several fake profiles of SNSD members set up, and used them to make himself look more "real". As a result, he had young women fawning over him, calling him "oppa", "appa" and "papa angel" (no word on how many of these were actual people or if they were other fakes he had created). He posted badly edited photos of himself and "official" ID cards (with blatant spelling mistakes - heck, some of the artists listed on the cards didn't even belong to SM), and generally acted like a creep. He was finally brought to the attention of SM, and appears to have been shut down.
It now seems that Thomas may have worked for SM after all, but the situation is very unclear.
People have mentioned that they did indeed see Thomas at various K-Pop events, but his behaviour was very odd (not wearing identification, wandering around and not doing anything, while other representatives of SM wore obvious badges and interacted with fans)...
Allegedly some of the young teens calling Thomas "Oppa" were fake profiles he'd created.
Someone from Globalone studios posted a message on his wall telling him not to associate himself with the studio. He promptly deleted it and blocked her.
Several months after the scandal was revealed, his profile is still up and he still has several fake profiles (SM has repeatedly stated that no member of SNSD has Facebook - so anyone commenting on Blevins' posts with the name of one of SNSD's members is fake), and is apparently dating/married to a woman who has changed her display name to "Seohyun Blevins". It's incredibly squicky - at the very least Blevins is abusing his position as an SM staffer, and he comes across as borderline pedophilic (regularly interacting with vulnerable underage girls and pretending he knows their idols to manipulate them).
The Unfavorite: Hyoyeon. She's not as conventionally attractive as the others according to others (Some fans call her ugly and useless - completely ignoring that she can dance rings around the rest of the group - and she was actually one of the more popular members of pre-debut SNSD), and SM doesn't seem to be helping matters any by giving her ridiculous hairstyles and less screentime in their videos/lines in songs than the other members.
European Sones Love Hyoyeon - One of the more noticeable things about the group's participation in the recent SM Town Paris Concert is that the French Sones in attendance cheered the loudest for Hyoyeon and favored her over the other girls.
Japanese/American Sones Love Sooyoung - Same for Sooyoung in Japan (she originally debuted there with a group called Route 0 and is in fact still fluent in Japanese). She seems to get more love internationally as well, which has lead to her becoming the co-centre and even seemingly taking over Yoona's dance position. She's also becoming a bit of an Ensemble Darkhorse, due to her strong improvement from their debut (arguably now among the top six vocalists), and her down-to-earth, witty and outspoken personality - she's often been mistaken for the leader of the group!
After their performance on the Letterman show, Sooyoung recieved the most attention/compliments (even some from celebrities such as Simon Curtis).
Unfortunate Implications - Why the release of the Tell Me Your Wish (Genie) EP was delayed. The original cover featured an Imperial-era Japanese fighter plane, and some of the girls' costumes featured stylized Nazi-esque insignia. Not the images to put on an album cover when you consider Japanese-Korean relations during World War 2.