Facebook's Places beams your whereabouts for all sorts of purposes
After clicking on the new “Check In” button, based on the coordinates beamed by the phone, the Facebooker will be shown with a list of prepopulated places in your location (like a beer dive, or the Library of Congress) and will let you choose where to check in. If the place you are at isn't on the list, you can search for it or, say, if it is an Iranian uranium enrichment plant, you can add it manually.
Privacy concerns are nothing new for Facebook, so the guys have taken some care to limit the app by default only to your friends. The not-so-good part is that your friends can tag you and check you in themselves, and you have to keep denying the nagging confirmations. The worst part is the function “People Here Now”, that allows you to see what fellow Facebookers said they are working late, but have checked in at the Yankees stadium instead.
It is not a bad feature to have, and the localized information you share/consume might prove valuable to check out the amazing gravy at Aunt Rosie's diner from your friend's last Route 66 roadtrip. You will certainly turn the feature on for that Euro vacation your parents will pay for when you graduate, but might want to tone it down for the binge-drinking bar hopping night if you are not yet 21, since the service is only available in the US for now.
We were unable to determine if you have to still follow your friends' whereabouts if you have switched Places off, but they are checking in at locations, as the service wasn't active on last try. Thus, please let us know if the morning trips to Starbucks of your more annoying friends start popping up like daisies on your Facebook page.