It doesn't mean anything, it's just a scary sounding letter.
Lawyers are skilled negotiators, part of negotiation is making it seem like they have a case especially when they don't. If Facebook had a case he'd be served and/or the police would be at his door.
A TOS violation? What are they doing to do? Turn off his Facebook account?
it's a way to free the judiciary of time consuming cases. before someone with a lot of money that wanted to harass some poor bastard would take him to court on any frivolous charge and crunch him on the weight of a legal defense. That was fine and worked just fine. but it was taking too much time of the judges. So they came up with the cease and desist letter. it works the same, the rich can continue to harass the poor, but no judge have any extra work. win-win!
