When Facebook launched Places, the social network’s long-awaited location-sharing feature, in August, it was accompanied by a couple of key assumptions. One was that 800-pound gorilla of the social networking space, with its 500 million total users and 100+ million mobile users, would take the check-in mainstream. Another was that the launch of Places signaled the death knell for foursquare and other location-sharing services. But as it happens, the reports of foursquare’s death have been premature. In fact, since the launch of Places, foursquare’s user base has continued to surge, growing from 2.6 million on August 12th (according to a tweet by CEO Dennis Crowley) to 4 million on October 21st. If it continues at its current pace, foursquare is projected to top 5 million registered users by the end of November.