What does Caesar's ghost symbolize?

I always thought that Caesar's ghost was an ominous sign for Brutus. Brutus really did think that he did the right thing to prevent Caesar from becoming this omnipotent dictator. Unfortunately for Brutus, not everybody has Rome's best interests at heart. The ghost symbolizes a bit of payback for Brutus. Marc Antony is about to turn the tables on Brutus with his famous speech. After that Brutus's days are numbered before he becomes a ghost himself.