Furthermore, just because you can link people together, it doesn't mean that knowledge is actually valuable. The only social network you can link to Venmo currently is Facebook. The only other way to "discover" contacts/friends is by uploading your contact book to Venmo's servers.

But a surprising number of people will pay for instant transfer(almost all of that 300m probably comes from this), and the debit cards they get to take in a portion of the merchant transaction fees. They’ll probably be profitable off that, with p2p as a loss leader to drive installs