Boston or Silicon Valley?
sethg: I'll repeat something I said here a while ago: the startups I've encountered in Boston (including my own employer, MetaCarta) tend to do B2B or government-contracting work, often bootstrapped with consulting or SBIR money.  The Valley startups I've read about seem more focused on consumer-facing applications.  So if you have a preference for what kind of product you want to be contributing to, that may affect which city you should live in.