TOS means "Terms of Service". When users get too rowdy
some people report them to their Internet Service Provider
(a.k.a. ISP) or hosting service and if the user gets their account canceled,
people say they were TOSed.
"Because of his post he got TOSed off LiveJournal"
An old America Online term. If one were to act up in chat room, a moderator could TOS you. It was similar to a kick, except AOL would disconnect, and every member on your account was notified with an e-mail. Multiple TOSes could result in losing your AOL account.
What happened to that one guy?
He was acting up, so the moderator TOSed him.