Dodgeball: Currently rolled out in 22 U.S. cities, and with about 15,000 users, dodgeball is the American MoSoSo standard-bearer. It works, explained founder Dennis Crowley, by having users check in with text messages announcing where they are. Then, because dodgeball maintains a database of hundreds of nightspots in each city, anyone on a user's friends list who is within 10 blocks gets a message that his or her pal is nearby. The service also has a "crush" feature. Users view profiles of other members and designate ones they'd like to meet. If the object of a crush is nearby, he or she gets a message to that effect. The system maintains privacy by identifying users only by screen names. "I can't tell you how many people I've met through this," said McGunigle. "It has not only simplified my socializing habits, but has allowed me to meet people I would not have met otherwise."