Actually, Rob Johnson just didn't like having a shitty completion percentage. I remember watching plenty of his games where he'd just take the sack and risk getting injured, instead of throwing the damn ball away.
The one thing that's wrong with Vick, is that he gets in that tendency where if the #1 guy isn't open, then he should take off running. Fuck, Vince Young hasn't even been doing that so much since coming into the NFL... in his rookie year.