The NFL implemented a rule before the 2009 season in which players, coaches and football operations personnel are allowed to use social media (like Twitter and Facebook) up to 90 minutes before kickoff on game day and after media interviews following the game.
Owens missed the deadline by 30 minutes, tweeting at noon on Sunday just before kickoff against the Buccaneers. Owens tweeted "A lucky fan wearing my jersey 2day will get a signed football by Me & Ocho Cinco! My asst will pick U out!! Good luck!" Even though the Tweet had nothing to do with the game, rather giving something out to a fan, this is still a violation of said league policy.
On Friday, Terrell Owens was fined $5,000, according to Adam Schefter, by the league for violating the league's social media policy.