Obama has people threatening to kill him every day, too. Members of congress get death threats all the time. There was a case a while back where a high school basketball player kept taking cheap shots at the opponent, it was caught on camera and put on Youtube. He received death threats, too. People are big talk, little action. Plus, this country isn't like it used to be. It's not every day, or every month, or every year, or even every decade that you see a lynch mob take somebody out.
Zimmerman should be fine. He's got a lot of supporters too, you know, and he'll get police protection should he be found not guilty. I hope he isn't, because if you're really against vigilante mentality, you'd oppose Zimmerman's actions in the first place. Nobody ought to pretend to be a police officer, or a judge or a jury.
Case in point - even the Westboro Baptist Church isn't the target of violence. If Fred Phelps can survive, so can George.