Foursquare takes lead in where-am-I apps

One year ago, the founders of Foursquare stepped onstage before a tech-savvy crowd in Austin, Texas, to announce their concept: a smartphone app that lets you tell friends where you are.

Now, as Foursquare's entrepreneurs head back to the South by Southwest Interactive (SXSWi) festival, they've hit a half-million users of their buzz-creating mashup of social networking and mobile games.

Foursquare has taken the lead in the festival's "location-based wars" as other upstart applications attempt to leverage SXSWi buzz to match the New York-based company's rapid growth and horn in on a burgeoning market. "We left South by Southwest [in 2009] with 2,500 users and had nothing going on all summer," Foursquare co-founder Dennis Crowley said. "It peaked and then dropped. Then we started getting a little press, and it just took off."