Presumably, Swarm didn't decide arbitrarily on "coins." We're guessing that eventually they'll be used to buy things, virtual or otherwise — you can easily imagine coins being used to cash in on discounts at locations you've been frequenting. At the very least, coins bring back even more of the gamification elements that old Foursquare users are used to. And don't worry: Foursquare tells us coins aren't going to turn into something you buy with real money; this isn't meant to be the start of in-app purchases. The update is launching today for iOS and Android, with a Windows Phone update coming "soon."