Quarterbacks, even when they break the pocket, should be treated differently from an average running back.
I can't say for certain that it applies in the NFL, but I know for sure that in NCAA when a QB leaves the pocket he loses his protection and becomes a runner like any other player would be.
That is how it should be as well. If you go outside the tackle box you are a runner, not a passer, for rules. You still get roughing the passer but that is about it, so if you are running, expect to get hit.
As I said, the NFL rules may be different, they are in general far more protective of the QB and prohibitive of contact than college rules. Honestly, if the NFL does lockout for a whole season I wouldn't be shocked if NCAA football takes over, it's a better product right now as far as allowing the game to be played and to be honest I find it more exciting for the most part, if they'd just address the whole cupcake scheduling issues it would be better than the NFL...