Facebook has taken the wraps off Facebook Places, its location-based service for mobile phones. It follows the principle popularised by Foursquare of checking in to locations, and is accessible via the Facebook HTML5 mobile site (touch.facebook.com) or via the Facebook iPhone app.

Users can select their location via the list that appears when they select the ‘Places’ option, or if it’s not listed, search for it, or add it themselves. After checking in, the check-in will create a story in the user’s friends News Feeds and show up in the Recent Activity section on the page for that place.

Only friends of a user can see them they visit or are tagged at a place, unless they have specifically set their master privacy control to ‘Everyone’. Users also have the choice to set more restrictive customized settings.

When a user checks in, they can tag friends who are with them, so long as their friends’ settings allow it, and post an update along with the check-in to tell people more about what they’re doing. The ‘People Here Now’ section enables users to see others who are checked in at the same place. This section is visible for a limited amount of time and only to people who are checked in there. Users who would prefer not to appear in this section, can optout in the privacy control settings. Users can also choose whether or not to share their location when they check in at a place, and when a user is tagged, they are notified.

Users can also choose to share their check-in information with third-party applications that build “interesting experiences” around location, such as travel planning. Applications must receive the user’s permission before gaining access to this information.

Facebook Places is available initially in the US only, but in the blog post announcing it, the company says it expects to make it available “to more countries and on additional mobile platforms soon”.