Other recent, sizeable New York exits include Buddy Media, which was acquired by Salesforce for ~ $690 million and OMGPOP, which Zynga purchased for a ~ $200 million.
The exits mean more capital to spawn companies and retain talent in New York. Tumblr was the result of an exit its founder, David Karp, was a part of in 2006. He was head of product for UrbanBaby when CNET acquired it and he used the capital to launch Davidville, a hub for his creative projects.
Tumblr won't be the last big exit New York sees either. Other valuable companies that are growing quickly include 3D printing company Makerbot and project funding site, Kickstarter.