Facebook has today launched its new geo-location service facebook Places (in the US only at first).
Is this goodbye to Foursquare? Maybe not, but, it will certainly be Hello! to new privacy panics by the mainstream media.
And no, updating your facebook page is safe, this is a mobile app, you have to request.
Whatever - formerly New Technologies for Libraries Blog 
Initial responses seem to be focusing on privacy concerns (not surprisingly): http://www.aclunc.org/issues/technology/blog/facebook_places_check_this_out_before_you_check_in.shtml
I am just glad the geo tagging and location based social networking has given us a nice new word to use ‘cybercasing’ http://www.wordspy.com/words/cybercasing.asp
cf. last year: http://xkcd.com/596/, further ‘cybercasing’ has been around as a concept since answering machine messages announced people were on holiday.
Social geo-location services have some interesting potential, especially in the marketing area. Based on the providers, there is no grounds to make any sort of privacy assumption, so I guess it comes down to what level of privacy the public decide they actually need (and how long it takes someone to develop a compelling service implementation).