Facebook on Wednesday threw the switch on a new feature that lets US members of the social networking service share their whereabouts with friends while on the move.
Facebook Places marks the firm's hotly anticipated first step into "location-based" services that have been catching on with people who own smartphones equipped with satellite position tracking capabilities.
"Starting today, you can immediately tell people about that favorite spot with Facebook Places," said Places product manager Michael Eyal Sharon. "You can share where you are and the friends you're with in real time from your mobile device."
Facebook members can "check-in" at restaurants, bars, or other social venues and let their friends at the social network instantly know where they are and with whom.
A Places application for iPhone handsets was released, and social network members with smartphones with Web browser software that supports geo-location and HTML5 could use Places at the mobile website touch.facebook.com.
"If you are not in the US you can still see if friends are using it here but you will not be able to check-in," Facebook founder Mark Zuckerberg said at a festive Places launch event at the firm's headquarters in Northern California.
Facebook said it plans to eventually extend the feature to all smartphones and to the social networks more than 500 million members worldwide.
As if anticipating backlash that seems to come with each change at Facebook, executives and engineers there stressed that privacy was being respected and that users control how location information is shared.
Privacy advocates have accused Facebook of failing to properly safeguard information members post to profiles, and adding people's location to the treasure trove of personal data is likely to intensify the debate.
With the rollout of Places, Facebook began making tools available to developers interested in crafting applications that take advantage of the new feature.
Users would have to grant an application maker permission before any data regarding their whereabouts was shared, according to Facebook engineer Ben Gertzfield.
Location-based social networking services Gowalla and Foursquare, which have been competing for dominance in the new but rapidly growing arena, were among the developers treated to early looks at Places.
Gowalla and Foursquare members that "check-in" places, letting their chosen circles of friends at the respective services see where they are, have been able to automatically update Facebook profiles with the information.
"This validates that we are onto something," Foursquare vice president of partnerships Holger Luedorf said at the Places launch event. "We definitely want to help people connect their online and offline worlds."
Startup Yelp that has attracted millions of users that share opinions of hotels, restaurants and other establishments promised a Places application for iPhones and Android-based smartphones will be out on Thursday.
Yelp is working on "augmented reality" that would enable people to peer through camera lenses of smartphones and see graphics indicating where Facebook or Yelp friends are in areas, according to Yelp products director Eric Singley.
"We think this is a really good starting point," Zuckerberg said of the Places launch. "You can imagine a whole world of things that can be built."
He said Places was starting out with a focus on "making it so you can share where you are and who your are with and see who is around you" and that Facebook will build on it from there.
Zuckerberg said it was yet to be determined how revenue would be generated from Places, but location-based services have proven potential when it comes to targeting advertising or promotions that users happen to be near.