PayPal (NASDAQ: PYPL) introduced Pay with Venmo about two years ago. Pay with Venmo takes all the functionality of PayPal, but allows consumers to pay merchants using their Venmo account instead of a PayPal account. It's another way for PayPal to take share of the market and leverage the growing user base of its free peer-to-peer payments app.But until recently, Venmo's monetization efforts hadn't really caught on.