The celebs employ ghost writers for managing the web stuff. the twitter and facebook thing is for promoting their films and brands. Check this out it explains how britney spears and majority of the other celebs have hired a team of writers and web marketing ppl who manage their accounts. http://www.nytimes.com/2009/03/27/technology/internet/27twitter.html
Btw, good to know you’ve finally figured out they’re humans.