Neopets has the Lever of Doom. The text reads "There's a strange lever sticking out of the space station wall, with a notice that reads, 'DO NOT PULL'. So you probably shouldn't pull the lever. You can if you want. But you shouldn't." The link reads "Pull the lever anyway". When you inevitably do? "Oh no!! An evil mechanical hand emerges from a panel and steals 100 Neopoints from you!!" The worst part is that it's Schmuck Bait with a purpose — there's a teeny-weeny chance that you'll be granted an exclusive avatar when you push the button. Users have been known to blow 80,000 Neopoints — 800 pulls — or more getting it, the lever laughing at them the whole time.
The UK Cartoon Network website had a large red button featured in the top banner that said "DO NOT PRESS". It was also introduced in the site's homepage intro "Just don't push the big red button". Cue an arrow pointing to it.
The website for My Parents Are Aliens also had a button in its side menu which when you rolled over it highlighted in red and a voice said "Do not press" (and was labeled accordingly). The question is, what did happen if you pressed it?
One of the random boxes in Warehouse 23 contains a laptop that, when picked up, types the message "Do you want to continue? Y/N" Choosing "yes" just makes the screen go black until you futz with it again. Choosing "no" results in... your heart stopping. Well, you did say you didn't want to continue...
For one day Twitter was cannibalized by a "Don't Click" hack that, upon clicking a button, sent a Tweet to your followers with the link to the button and a "Don't Click" warning. (Read all about it.)
A practical joke that had a switch conveniently labeled "Magic/More Magic" would "magically" crash the computer it was attached to if it was switched from "More Magic" to "Magic". It wasn't supposed to do anything— the switch was completely inoperative. And yet, every time it was set to "Magic"... Maybe it won't crash the computer this time.
The xkcd games forum had a thread titled "Post here and be banned". Everyone who posted in the thread (except the founder) was banned. After a point, anyone who posted was permanently banned.
4chan's "/b/" imageboard had a similar thread, with the site's founder and admin, Moot, taunting the /b/-tards to post in the thread and be banned. They were. Amusingly enough, Moot himself posted in the thread to laugh at the shmucks who had taken the shmuck bait... Only to be banned himself.
The Facepunch forums have Idot Culls semi-regularly, which often consist of an admin or moderator creating a thread with an OP something along the lines of "do not post in here or you will be banned" or some other very specific instructions with a clear threat. If you do post in it you get permabanned but that doesn't stop idiots from doing it anyway, hence the name "idiot cull".
The TV Tropes Wiki has its share of Schmuck Bait:
Every single external link on the Ear Worm pages is an invitation to get a song stuck in your head.
On the Something Awful forums, anyone who posts a thread is explicitly warned not to use one of the three "Mod-only" tags. Anyone who chooses to ignore this is automatically banned, and the reason for said banning is "Breaking the rules with a *adjective* thread!" To further drive the point home, one of the mod-only tags says "Ban Me"—and yet people still do this. (For extra schmuckiness, it costs $10 to register on the forums, and a regular ban or autoban enables you to re-register... but you have to pay another $10 to do so, plus any custom titles, platinum status, etc., that your pre-banned account might have had if you see fit to do so.) As of this writing, there have been about 17,800 total bans in the last six years or so (normal bans, autobans and permabans); 3554 of those bans have been autobans.
It's rather common on auction sites for someone to put up the box of the console (Xbox or PS3) for auction-just the box, nothing else inside it (such as, say, the game console). They'll even clearly state in the writeup that there's no Xbox inside, but every time a herd of bozos will invariably bid on it, then the winner gets all angry afterwards once the realize what they actually bid on.
Most often, however, the fact that it's only a box, while stated plainly, is buried in a wall of text. But in any case, if a complaint is filed then most auction sites will side with the buyer because such listings are clearly intended to deceive prospective bidders.
Similarly, some textbooks come with a smaller book that's an answer key or study guide. This study guide has the same ISBN and edition number as the textbook, so students buying used textbooks online should be careful.
This is done with Tarot decks and similar "box of items with book" sets. The book has the same UPC code on it as the kit, so it's not their fault you didn't specify. Sure.
And a book's first paperback edition is still technically a first edition.
Anything that says "Do not look up Goatse" or "Do not look up 2 Girls 1 Cup"!
Don't go to lemonparty.org, either.
Recently, 4chan blocked the random board to outsiders by making the page a completely black screen offering the advice "Press Alt+F4 or Ctrl+W to view board." As any well-versed computer user would know, Alt+F4 and Ctrl+W are "close window" and "close tab", respectively.
Reading the comments on the game "Flight" on Kongregate, about half of them are warning against throwing the plane backwards. The other half, naturally, are people commenting about what happened when they do.