I just listened to a talk by Ori Brafman in which he mentions that one of the most important factors in professional collaboration and friendship is physical closeness. MIT dorm students were twice as likely to be best friends with their immediate dorm neighbor (6 meters away) than with the dorm neighbors two rooms down (12 meters away). Professional collaborations followed the same pattern. Y Combinator likes to see founders share an apartment. There's probably a lot of value in simply being physically near other people with similar interests.