What's great for me working at Facebook for the last three and a half years is that I can get that productivity reinvigoration by switching teams and solving new problems, without having to learn quite as much stuff as I'd need to at another company, and keeping my existing reputation and also my friends and work acquaintances.

I've worked on at least four teams since I joined (and a few smaller projects) - ranging from spam fighting systems, search infrastructure, internal infrastructure management systems, and now on the CDN team.