They are on the inside of all hoodies given to FB employees. After the story showing this came out one 'smart' employee or ex-employee put his on ebay. Bidding is up to $4k
ebay auction -
http://cgi.ebay.com/ws/eBayISAPI.dll...t_500wt_ 1140
pic of the logo -
http://twitpic.com/1tzvdg