But SF hasn't, or at least I can't think of any big startups in the city, particularly that have stayed post IPO. Twitter is probably the largest at roughly 30

But SF hasn't, or at least I can't think of any big startups in the city, particularly that have stayed post IPO. Twitter is probably the largest at roughly 300 people. And honestly, do the math: if Twitter goes public for $10B, and they've given 20% of the company as options to execs and employees, thats 2e9 * $.015 = $30MM. That would sure ease the pain of moving out of the city while simultaneously paying a lot less rent.