I spent about 5 years at Google starting in 2006. When I arrived I was assigned to one manager, but I wasn't _super_ excited about the project. A week in, another manager offered me another opportunity and got me permission to transfer. Problem solved.

A couple years later, a new hire got assigned to a team I was on. He was a little bummed because he'd really had his eye on another project. So we talked to our manager about it and he was allowed to transfer to the team he'd been hoping for.

I have more anecdotes like this, but the long and short of it is that in my experience Google is a lot less capricious and uncaring an organization than you imagine.