CB Cortland Finnegan followed Jeff Fisher to the Rams, but in his second season in St. Louis he's been terrible and injured. He's due $6 million next year, and would count for $10 million against the salary cap. Since this is the NFL and contracts mean nothing, the Rams sure as hell weren't going to pay that. So they came to him with some options for a pay cut. He decided to tell the world, "No thanks."
That news apparently came as a huge surprise to many members of the Rams. According to Ian Rapaport, Finnegan told Fisher and some other folks in the front office, but then immediately sent out the Tweet, ensuring most of the Rams staff found out the same time you did. (Well, not you. You don't follow Cortland Finnegan on Twitter.)
Finnegan told the people who needed to know, so he's in the clear. And it's nice to get a reversal of the usual process, where a player finds out he's been cut or traded from the media before his team tells him.