LulzSec hasn't shared a reason for the attacks just yet, but we can only guess it's, as they say, "for teh lulz."
Update: The group has gone after Riot Games' League of Legends servers as well. Attempting to log in to the game gives a "server busy" message, though there's no official word from the company yet.
Update: Statement from CCP after the break. EVE Online still seems to be down.
Immediately, these services were taken offline. As an added precaution, all of CCP's infrastructure was disconnected from the public Internet.
The CCP Security team is conducting a thorough investigation to determine exactly what happened and how, what the possible impact may be and, first and foremost, assuring that any personal information of our customers remains secure.
More information will be released as it's available.