Harvard CS professor and blogger Matt Welsh just announced that he will be leaving Harvard to join Google.
His reasons sound similar to my own motivation for leaving Dartmouth 12 years ago for Microsoft:
The cynical view is that as an academic systems researcher, the very best possible outcome for your research is that someone at Google or Microsoft or Facebook reads one of your papers, gets inspired by it, and implements something like it internally. Chances are they will have to change your idea drastically to get it to actually work, and you'll never hear about it. And of course the amount of overhead and red tape (grant proposals, teaching, committee work, etc.) you have to do apart from the interesting technical work severely limits your ability to actually get to that point. At Google, I have a much more direct route from idea to execution to impact. I can just sit down and write the code and deploy the system, on more machines than I will ever have access to at a university. I personally find this far more satisfying than the elaborate academic process.
For me, it is much more interesting to actually *do* things than to write papers about hypothetically doing things. Academia doesn't always do a great job at supporting doers, which I think is a real shame, since practice often drives theory.
In any case, Google is a great environment for researchers with the right mindset. Welcome aboard, Matt!