I don't live in SF so this may be a bit ignorant, but it's possible the market is simply saturated out there. You may see heaps of opportunities, but you may not be seeing a horde of people who are actually looking at the same heaps of opportunities and are better positioned for them or simply luckier than you are. 4 years of mobile development seems to plant you pretty strongly in the mobile realm, as you would have gotten on board back when OpenMoko was still relevant. Are you looking to switch away from that? That might be rough in a saturated job market.

Are you currently unemployed? That can also send a pretty rough message and make it harder to get a job than it would be otherwise.