For those who haven't yet heard of it, Venmo is a handy app that facilitates payments, not unlike PayPal. It's especially useful for friends to pay each other for bills, like splitting a dinner check, putting in your share of the rent, and paying a buddy back for spotting you a few beers. Just find your friend, type in the amount you want to send, and voila -- they're paid.
The only problem is, the payment doesn't quite happen as instantaneously as the app says. There can be a delay between getting that "cheery green plus sign" in the Venmo app and getting the funds into your bank account. And scammers are taking advantage of that loophole to take advantage of trusting sellers.