I'm not sure it's possible for a single company to provide advancement opportunities for most of its ambitious mid-level contributors. Mathematically speaking it makes at least as much sense to play the wider job market looking for a succession of "perfect fit" jobs for yourself every few years rather than sticking with Google and continually trying to win a shot at a series of slightly more prestigious positions.

Obviously if you were part owner of the business things would change considerably, but not everyone has the risk tolerance for that - it helps to be single with cash in the bank.