Koobface: http://www.snopes.com/computer/virus/koobface.asp
http://vil.nai.com/vil/content/v_148955.htm
http://www.securecomputing.net.au/News/154631,koobface-spreading-through-thousands-of-ip-addresses.aspx

Facebook info: http://www.snopes.com/computer/virus/facebook.asp
http://www.snopes.com/computer/virus/fbi-facebook.asp

Greeting card: http://www.snopes.com/computer/virus/friend.asp

Feel free to add more below.