my facebook account was disabled

Yesterday, one of my friend buzz me on Yahoo! Messenger and say: "my facebook account was disabled".

Although this is weird, i tried to google some reason for facebook to disable user account, and what I should do if my facebook account was disabled.

There are many discussion ever websites/forums discussing the same topic: my facebook account was disabled
So many clues and hints suggested, however, nothing can help to reactivate a disabled account.

I believe, the only way to prevent facebook admin disable your account is safe facebooking

Any useful clue?