Foursquare, the service that allows people to text to the world when they've arrived at the corner donut shop (that's called a "checkin") just passed the 100 million checkin mark, Mashable reports. That's not registered users – more like 100 million Facebook updates – but it says something about the growth in geolocation apps' and games' popularity. "Foursquare has experienced massive growth in … [Read more...] about Video Barbie tight with fast-growing Foursquare