Most iPhone users with the newest version of the Facebook mobile application can access it. More details and potential issues will emerge as more people start using it, but here's the deal so far.
Most people have seen location on Facebook through separate location-based social networks. With Foursquare, for example, it's possible to push your location, with your comments, from its separate platform to your Facebook profile. The difference between Foursquare and Facebook Places is that Places is on the Facebook platform.
Facebook, as usual, has its large network in its corner. When I've checked in using Foursquare, the application only acknowledges friends that I'm with who also have checked in using Foursquare.
Facebook allows tagging (similar to photo tags) of friends; they just need to have a Facebook account.
Foursquare and Gowalla have more features. Facebook will have a record of something a friend wrote that will be tied to a place, but Foursquare has "tips" tied to places and Gowalla has "trips."
As usual, Facebook's default settings for Places are loose. It's set to friends only, but that's a little misleading. It appears people who are not your friends (Facebook blog post says people you might want to "meet") can see that you're checked in somewhere if they are checked in there as well.
With the new Facebook platform, applications or Web sites can pull in certain information about friends when you use it.
This means that even if you're not using an application or service, your information could be included if a friend is.
Here's a road map to where the privacy settings to Facebook Places are located:
Places you've visited: Privacy > customize settings
Inclusion in "People here now" (default is checked yes): Privacy>customize settings
Places visited visible through friends' applications or use of Web sites: Privacy>Applications, Games and websites>Info accessible through your friends>Places I've visited.
Ultimately, like other location-based social media, you control where you check in -- it's not a tracking device.
Facebook Places can be a useful tool to interact with friends, but consider what you're comfortable with sharing and adjust your privacy settings accordingly.
Interact on Twitter @SarahDayOwen.