I'm working at a YC startup, but the rent in SoMa is insane, so my wife and I decided to try and split a 2BR place. We thought we found a roommate, but unfortunately, they pulled out. So we're moving in less than a week, and haven't been able to find someone else yet.
Anyway, if you're interested, please check out my post on /r/SFBayHousing: http://www.reddit.com/r/SFBayHousing/comments/1rer9s/offershare_looking_for_a_roommate_or_couple_to/
I'm sorry, I know this post is a bit unorthodox. Maybe it should have titled it "How I'm trying to pay less rent as a YC startup employee in San Francisco".