I think for some people its an obsessive need to tell anyone who will listen about every minute of their life... when I first signed up to twitter I started to 'follow' loads of friends, family and business people.. gradually I thinned it out and now am very selective...
Its great for instant news or updates on my business subjects and professional aspects. Its also great for instant updates on various sports events... I also follow my favorite radio station and programmes. That can be fun.
Its rubbish when people feel the need to bitch or to say 'just going out to get some more bread, won't be long'...