The Air Force is warning personnel that while geolocation features like Facebook Places or Foursquare may be a great way to let your buddies know where you're having lunch, you shouldn't use them in war zones. "Careless use of these services by airmen can have devastating operations security and privacy implications," the Air Force warned on its internal website earlier this month. The Army plans to circulate a similar warning to troops about the social media features, AP reports. (More Facebook stories.)