Must have pissed off Anonymous somehow. Everyone knows that they are responsible for all hacks.
HACK THE PLANET
Its more likely to be Something Awful who hacked it. Because MP was an idiot and challenged them.
Wait, so a DDOS attack is a "hack" now?
Please go to
http://mpex.coinbr.com, a web proxy to the MPEx backend, and tell me if it's been "hacked".