I think a big factor of "why now in NYC?" was the recession: with firms collapsing, job security at an all time low, and dismal salary and bonu$ prospects, all the talented individuals that had flocked to Wall Street and hedge funds were now leaving or forced out. This yielded two things: smart, networked, tech savvy individuals that had monetary padding (via a few years of pulling down salaries and bonuses back in the gilded era) to bootstrap an idea and the network to tap into AND investment oriented folks looking for opportunities that offered a better ROI than the dismal public capital markets'.