The way things are going, maybe it's not a bad thing to play with a bullpen. Both guys keep getting experience, and maybe one or the other has a hot hand on some particular day, or maybe they both play a little more relaxed coming in off the bench. Also, if it is common to make a switch, maybe the stigma is lessened and they don't feel so much like they're "looking over their shoulder".
These were all his choices. He chose to keep Leinart around for 3 years and then cut him a week before the season. He chose not to look into a new quarterback when he knew Warner's time was limited. He chose Anderson over Leinart. He chose Hall over Anderson. He chose to waffle back to Anderson. His choices about the quarterback position (we won't get into his play calling) have turned a team that should have a chance at a deep playoff run into a travesty of its former self.