Digital 4M Users Check In to foursquare By David Cohen|October 22, 2010Share By David Cohen|October 22, 2010Share Checking in is the in thing, as foursquare co-founder and CEO Dennis Crowley told GigaOM the location-based mobile app topped 4 million users. foursquare reached 1 million users in March and 3 million in August, according to GigaOM, and Crowley said it took just 50 days to go from 3 million to 4 million. Adweek Adweek