David Herbert apparently attracts this kind of production with all his works except Living With Insanity. Tnemrot was supposed to be a print comic and was written in late 2008, going through seven artists before Tatiana Lepikhina joined and is now a webcomic. Gemini Storm was also written at the same time, came out in March 2010 and the second issue is still expected to take another month or two before being released. He has also mentioned other projects that haven't gone anywhere due to artists dropping out or simply disappearing.
The non-Cliff Notes description: The story was meant to be a three act event to herald the arrival of Amazing Spider-Man #400. However, no one seemed to have an idea on what to do before hand and went with the idea after it was given and championed. Things spiraled out of control because of the four aforementioned problems: Marvel, via Ronald Perelmannote the man who would end up bringing Marvel to the brink of bankruptcy., wanted a storyline that would rival Age of Apocalypse and, going with a "profit or die" mentality note meaning that if your title didn't bring in the money, it and you were given the axe, the marketing department held a lot more clout than anyone else: instead of a set series of stories, marketing demanded that they stretch the story as long as possible. That meant one-shots, mini-series and extra long events. Bit by bit, creators got fed up and walked out as the story grew more and more convoluted.
Anything that isn't part of the mainstream Marvel Comics tends to suffer from this. One of the more documented ones was The New Universe. Touted as "The World Outside Your Window", the franchise fell apart from the beginning - writers tossed in 616-type elements (aliens, powered armors, etc.), financial backers pulled out before it even started, and people were too engrossed by that slogan. Despite canceling half of the franchise and starting a massive storyline that started with the destruction of Pittsburgh, it never got off its feet and died nearly three years later.
newuniversal suffered an equally crushing blow when the files on Warren Ellis' laptop were lost when his hard drive failed. Marvel shuffled him on to other projects and newuniversal died an inglorious death.
Marvel 2099, which depicted a futuristic Marvel Universe as a Cyber Punk dystopia, wasn't the greatest, but when Marvel let go its editor-in-chief for that line as a cost-cutting measure thanks to its near-bankruptcy, many of its creators bailed due to their dislike of his replacement, leaving the series to limp to its end.
And while we're on that subject, anything done by Rob Liefeld, a master of the Schedule Slip. During the aforementioned Death Mate, Liefeld's contributions had passed so many deadlines, that an editor from Valiant had to go to Liefeld's house and refuse to leave, just to make sure that his work wasn't over a year late.
Sonic the Hedgehog always had a problem when it came to converting video game storylines into its largely different setting. However, two of the biggest screw ups came about via Sonic Adventure and Sonic Adventure 2. For Sonic Adventure, Sega gave Archie a copy of the game... untranslated, so they had to fudge a lot of the story. The original plan was to have the storyline run through then-all three titles - Sonic the Hedgehog, Knuckles the Echidna and Sonic Super Special. However, just before the storyline started, the Knuckles comic got cancelled, forcing Archie to cram all of the Knuckles stories into the Sonic issues as back stories.
For Sonic Adventure 2's story, the big problem was that Sega was insistent on Archie creating a tie-in into the game. Archie's solution? Just do enough to whet people's appetite and go get the game. Still was enough to ruin a side-by-side storyline that had a cosmically-powered Knuckles altering Mobius drastically.
From Sonic Adventure 2 onwards, most adaptation storylines ended up just usually being short teasers following the issues main story. The teaser game stories have boxes that clarify whether the game in question is to be taken as canon in the comic's universe or not.
As well, the latter issues of the Ken Penders' run was filled with problems, mostly due to the fact that he and fellow writer Karl Bollers were at each other's throats and attempting to change certain parts of their ongoing story, leading both of them to quit and be replaced by Ian Flynn. This has boiled over into the current legal drama between Archie and Penders, as the latter is seeking to take back every last character he's created for the series, most likely leading to the greater use of Sega-based characters.
The Penders Case has, as of December 2012, reached a settlement with notable ripples in the comics. Both the Endangered Species Arc in the main comic and the Chaotix Quest Arc in the Sonic Universe spinoff had to go under emergency rewrites and art changes as a result. Fans are quick to note the blatant changes and are openly upset over the background politics so clearly disrupting the stories.
The wedding of Clark Kent and Lois Lane was this. The original plan was for them to get hitched in Superman vol. 2 #75. However, by this time, Warner Brothers was making plans to make a new live-action Superman series and asked DC to wait until they did their own wedding to do theirs. DC complied, but they just lost a year's worth of stories. At one of their "Super Summits", writer Jerry Ordway made his usual joking suggestion of "Let's just kill 'em" and it gained traction. We all know where that went. However, the wedding languished for four years while WB continued on with their series. At one point, DC actually separated Clark and Lois waiting for them and once the series FINALLY got to do their wedding - four years later - DC was quick to reconcile them and get them married.