Capulous on 18 June 2011
I've read a few things about this. It seems a third party site got hacked and they posted the email addresses and passwords from that site. Since many people use the same email and passwords for every site they visit; LulzSec told people to try them on other places to see if they worked. Here is an additional article regarding it:
http://www.cbc.ca/news/canada/prince-edward-island/story/2011/06/17/pei-lulzsec-personal-internet-accounts-584.html
Xbox LIVE was not hacked according to Xbox support. After what happened to Sony and many other sites, they would probably inform people immediately, if it did happen.
http://forums.xbox.com/xbox_forums/xbox_support/f/1234/p/23422/146733.aspx#146733
