Forget the fail whale, fail cat, or any other fail creature Twitter has rolled out to explain surges in Twitter traffic - it's a large scale Denial of Service attack. What's a DoS? Yeah, I didn't really know either. According to Wikipedia (the source of all knowledge on the planet):
...it generally consists of the concerted efforts of a person or persons to prevent an Internet site or service from functioning efficiently or at all, temporarily or indefinitely.
Basically, it's a huge effort by a basement nerd and his/her posse to eat up the allocated space of a website so that service slows down or dies completely. For Twitter addicts out there, this DoS might manifest itself in refreshing twitter.com every minute, or treating Facebook like their own private Twitter party. I even posted my first status update to Facebook for the first time in eight months this morning (it's my wedding anniversary, sue me).
Twitter now joins a rather illustrious list of DoS victims, including Mikhail Saakashvili, Pirate Bay and the Irish Government. I sure hope these DoS-ers (tossers?) don't live in the UK - it's against the law and carries a maximum of ten years in prison. Ouch.