Nicole found out the guy she was dating was already in a committed relationship. Abby learned that her ex had most likely hooked up with someone new, and Ben discovered that a long-ago casual fling had apparently developed a drug habit. The sleuthing tool that cracked these relationship mysteries was not a private investigator, but the peer-to-peer payment app Venmo. The mobile payment service, which processed more than $35 billion in payments last year, is a no-fuss solution for splitting the dinner bill after a night out with friends. But Venmo users have found it’s also an extremely effective tool for keeping tabs ... (full story)