Harbaugh probably thinking Colin had one hell of a game against one of the better defenses in the league, and if he can do that to the Bears defense, he should be good against average to poor defenses. But it is very risky. If Colin has a stinker of a game next week, wow, do you have a big can of open worms now. If you're losing, yeah do it, nothing to lose. But when you're winning, and this doesn't pay off in the next few weeks, whoa, there will be a ton of criticism coming down on Harbaugh.
I just have a question though, is this now official? I know Colin was taking 1st rep snaps in practice early in the week but Harbaugh had said nothing about who was starting the game.