Places is Facebook's stab at sharing locations with friends via GPS tagging; by tapping a "Check in" button and choosing a location near you, you'll be able to share your current location in your friends' news feeds. Your check-in will also show up on the location's Recent Activity page, assuming the location has a Facebook page. So, you can look forward to a lot of "Johnny Appleseed is at Target in University Heights" posts in your Facebook News Feed in the near future. Hooray? You'll also be able to tag any friends who are with you, and you can see other Facebook users at that location by checking the "People Here Now" section.
Places is currently only available in the USA (meaning that I haven't tested it), but Facebook promises to roll the feature out to other countries and mobile platforms "soon."
I like the idea of this feature in theory, but in practice, as soon as this feature rolls out in my country, I'll be scrambling to disable it. I've always thought of apps like Gowalla and Foursquare as the electronic equivalent of hanging a big sign in front of your house saying "I'm away from home, PLEASE ROB ME!" Add Facebook into the mix, a site already notorious for its questionable privacy record, and it's enough to send people like me into paroxysms of paranoia. Facebook spent over half their Places introduction post stressing that any information users share with Places is completely under users' control, but we've all heard that one before.