When all your friends used to be on bebo/myspace but one by one they drop and join Facebook. This is called the "Facebook Flu" or the "Facebook Fucker Flu". No longer do people go on bebo or myspace, so you resort to commenting yourself....
John: Hey, check my new bebo skin?
Peter: Are you stupid? It's all happening on Facebook!
John: Peter, you've got the Facebook Flu