i dunnno about you but i know what my friends are doin all the time and if it's something thats good then they let me in on it without using twitter. and famous ppl's job is to entertain us normal ppl so it's cool for them to tweet what films they gonna be in and how the production of a cd is doin etc etc. for the reg people it's easy enough to call or even text them.
The only reason I would have twitter is to recieve updates on celebs. Not updates like "Im cleaning my teeth now" and shit like that but updates on tours and albums and shit. Thats the only reason I can see for having twitter. Thats my story.