The Facebook page of The British Monarchy, Nov. 8, 2010. Queen Elizabeth has joined Facebook, adding a presence on the world's most popular social network to the royal family's accounts on Twitter, photo-sharing site Flickr and YouTube.
UrbanDictionary.com’s definition of “jump the shark” is:
a term to describe a moment when something that was once great has reached a point where it will now decline in quality and popularity. The origin of this phrase comes from a “Happy Days” episode where the Fonz jumped a shark on water skis.
The "Happy Days" moment has to be seen to be believed.
Today.com story: Britain's queen wins 100,000 fans on Facebook debut