Twitter users began receiving link coming from accounts they follow, links that were prefaced by the words "Don’t click". Needless to say, forbidding on the web is actually using reverse psychology to make the user to whatever you want him to. Don’t click naturally turned into “I’ll click and you can’t stop me!”.
As it follows, hasty clickers were taken to a web site employing technique called clickjacking. Twitter co-founder Biz Stone writes:
"[Clickjacking is]A vulnerability across a variety of browsers and platforms, a clickjacking takes the form of embedded code or script that can execute without the user’s knowledge, such as clicking on a button that appears to perform another function."
In Twitters case, this led to an avalanche of new message being sent across the service, messages that came from every user naïve enough to click the link. No actual harm was done, but the mishap prompted Twitter to submit an update which blocks the clickjacking technique.