Not OP, but I was wondering how they compare to ZeroCater, which is also YC-backed, feeds some big names like GitHub, Foursquare and Tumblr, and has all those billboards up and down 101.
Zesty also serves GitHub, and Zesty usually handles their events. There is a lot of business in town; more than enough to go around. And you don't need billboards to be a market leader.