Nova's comments are right on the money. I don't know that I can say it much better than he did. Outside CEOs definitely can be necessary to shake things up and get them on a more steady execution path. The culture of the company shifts when this happens and that is never a clean process. I experienced this at Tribe where all of us founders eventually exited.
I have to stress that this is not necessarily a bad thing. Sometimes founders should not stick around and that's just better for the company and the founders. More value is created that couldn't be otherwise.