Just a little theory for those who think that Red John is Walter Mashburn.
If Red John is indeed affected by acrophobia then Walter Mashburn can not be Red John. Remember the episode 2x12 where the Lamborghini of Mashburn falling off a cliff. Then we can see Mashburn approaching the edge of the cliff to watch the rest of his car without apparent fear. He probably would'nt have been able to do that so easily if he was really affected by acrophobia.