I was apparently lost in the shuffle, so when I contacted them a week before my start date to ask what was going on, they came back three days later with a single team.

I met with the team, and told my recruiter that I didn't mind working with them (though it's not clear what would have happened if I had). I was then given a form with room for a dozen teams, and asked to rank my only choice on a scale from 1-10.

If you asked for a team straight up, you basically didn't go through allocation.

You're right that anybody can ask for a team. In practice, most don't realize that they should be discussing allocation before they sign the offer letter, when they have the most leverage.

I know of people asking for and getting put on 'interesting teams' -- only to find themselves idiotically placed, in parts of a shockingly large team that make no sense given their backgrounds and motivations.

It's not the end of the world, but it makes for a tough first year.

I made some other points at http://news.ycombinator.com/item?id=2801866.

I was given a preference sheet to fill out after receiving an offer, and I was given my first choice, also. It seems there is quite a bit of leeway to change teams if one finds something else more interesting.

You had a bit more leverage going in than most, be fair.

I don't think I had more leverage than most (I came in off a failed startup, plus two years of work experience before that and a pretty mediocre GPA), and they gave me my choice of teams. I was allocated to Search, but the recruiter made it clear that if I had a problem with that, there were other teams - GMail, Docs, etc. - that wanted me and I could go there.