Hello again and welcome back to Fast Company ’s Plugged In .

If you owned a smartphone a decade and an half ago and were into cool new apps, there’s a more-than-decent chance you tried one called Foursquare . The best known of a then-new breed of location-based social networks, it let you check into places you visited in the physical world, and see where your friends were checking in.

One Foursquare fan quoted in an October 2009 New York Times article by Jenna Wortham called the ability to find nearby pals for spur-of-the-moment meetups “planned serendipity.” The app also included gamified elements that made it feel less like a utility than a form of entertainment, including badges and the chance to become “Mayor” of your favorite haunts.

For a time, Foursquare had plenty of competition from other check-in apps, such as Gowalla, DeHood, Brightkite, and Loopt (which was cofounded by a guy named Sam Altman). Inevitably, Facebook pounced on the trend, introducing a feature called Facebook Places.…