I see the need for it if you are a celebrity or a business but otherwise not really. Just seems like another one of those pointless things to have. "Snitching" gets thrown out the window the moment any form of violence comes into play.
Usually if I'm wasting time on the intranets I am baked, and having only 140 characters to express my thoughts at these times is just bologna! I end up spending WAY too much time trying to come up with short forms, abbreviations, where I can take out a space without being too inconspicuous, deleting punctuation and so on. On the other side of things, getting updates from celebrities is annoying. I really could care less if you're having lunch with your friends or if you "totes just bought a cute new bag" Needless to say, not a fan at all.
What's the point of businesses and celebrities to have twitter if no one else has a twitter? The only reason a business would market somewhere is if there is a target...i.e. normal everyday people