Why do people in relationships keep posting on Facebook what they are doing and where they are?

[big]That's why I've ever been on Fb and never will be. With some exceptions of course, those people remind me of the weird person who sends a Christmas letter to everyone they know bragging about how little Johnny lost his first tooth and found a quarter under his pillow. Oh what fun! I live to hear about those moments in other people's lives......Not really.