Just tried Yik Yak after reading this. In SF's FiDi, appears to be mostly dudes looking for gay hookups. Am I doing it wrong?
I live near a university, so all I see is drinking, smoking, classes, roommate drama, and hookups.
My guess is here there's isn't much for office workers to be sharing with strangers -- it's kind of a weird premise unless there's some specific city wide event like a parade or a terrorist attack. Thus the next logical reason for (gay male) strangers to interact is to hookup.