Mountain View-based Facebook has acquired Branch, a New York-based startup which develops a pair of mobile conversation and social networking applications (Branch and Potluck). Financial terms of the buy were not disclosed. The deal was reportedly worth around $15M. Branch will help staff up a new group for Facebook in New York City. Branch was backed by Jason Goldman, Evan Williams, Biz Stone, Ryan Freitas, John Borthwick, and Jonah Peretti, as well as other angels.