According to IDC analyst Aaron McPherson, social payments are increasingly on companies' radar.

Venmo also verifies users by requiring them to connect through their Facebook accounts, which McPherson said is an advantage over email-linked payment services like PayPal. "The thing about social networks is that people generally only have one identity," he said.

Like most other person-to-person payment services, Venmo transfers will be slowed down by the Automated Clearing House infrastructure on which they rely for non-credit card payments, McPherson said.

"I've yet to see a mobile payments system that doesn't use ACH," he said, "but you need to be careful with that because sometimes it takes two days to make a transfer -- and it can take 5 days."

Venmo is currently free for ACH transactions. Users get US$500 in credit card payments free, but then begin paying a 3 percent fee. Asked how the company would generate revenue, Kortina said that Venmo was currently focused on making its payment system "fun and easy." But he suggested that the app may eventually allow individuals to pay bars and restaurants, for example, and in that case Venmo would charge the merchants a small fee.