How come when The Rock got booed as a face WWE turned him heel, but they haven't done so for Cena?

I would go with Stone Cold and Brock Lesner. He was more like Jericho... he's very important but not the top draw. Cena is the top draw but for every boo he receive he gets 100 more cheers. I can really only think of one time he was booed out of the arena and that was ECW against RVeffinD. The fact that it was Cena was just the icing on the cake.