"Facebook Is Working On A Foursquare-Killer", http://www.businessinsider.com/facebook-is-working-on-a-foursquare-killer-2010-1
You can add location information to your Tweets, such as your city or precise location, from the web and via third-party applications. You always have the option to delete your Tweet location history. Learn more
"Facebook Is Working On A Foursquare-Killer", http://www.businessinsider.com/facebook-is-working-on-a-foursquare-killer-2010-1