Personally, I don't use twitter or Facebook - but especially twitter, I see no point too, I'm just plain not interesting enough for it to matter to most people what exactly I am doing when.
The hand full of times it dose matter to a few other people, it's much easier to just tell those few individually.
I can see the point of, and at times have used, public networks to communicate - but unless it is for a business, or selling something, excreta, I wold rather do it privately - example, I run my own mail server - I use a "free" mail account for anything public, my ISP mail for any true business transactions (banks, E-merchants, excreta), but the one I run personally, on my own computer - ONLY fairly close friends and family members use that one.....