I have said it before and I will say it again, only twits twitter.
Every leading news source online today has a twitter feed. Are they all twits? You seem to be only looking at it from a social point of view, where others use it as a business tool or as a source of information.
Initially when Twitter was released I felt the same way, that it was simply an overload of silly unecessary messages being posted by someone that had nothing better to do. But after trying it out for a while, I quickly realised how useful it can be, since twitter has multiple uses.
Do I post silly messages all day long? Not at all. But I do follow/subscribe to several of my favourite news sites' twitter feeds and then use the Twitterfox Firefox add-on to periodically display small blurbs of all the main news articles in the corner of my browser throughout the day. This keeps me informed (I am a news junkie) without actually having to visit those websites. So Twitter has become my own customised RSS feed; a primary news source.
As far as individual twitters go, since you can reply to anyone's tweet it makes group discussions easy because you quickly identify twitters with similar interests or you follow/subscribe to IT people you know and it turns into a proper discussion, with the ability to automatically post short URLs (shorterns long website addresses using tinyurl etc.) as well as pics (TwitPic) that are shared.
As an example, I use this MyBroadband site's twitter feed to popup any new headline articles in my twitterfox which allows me to read or visit the forum thread directly from the feed in the corner of the browser, instead of loading the website every time to see if there's anything new. Therefore never interrupting what I'm currently doing.
I also use Twitter to gain and share knowledge, because you can post a question e.g. about something very specific and someone out there will reply to it quite quickly. It's like a global forum without trying to be one. Again, it's about 'following/subscribing' to the right people. Twitter is also searchable; you can find any twitter, feed or releated comments just like you would search an online forum.
The bottom line is that if you subscribe to people's Twitter feeds who have have nothing substantial to say, contribute or share; then yes, it becomes a case of twittering twits.

Especially those who only use Twitter to have the odd silly chat (nothing wrong with it, I'm just not into it). Very easy to avoid those since you simply don't subscribe to those Twitters.
But there are a lot of useful, informative twitter feeds out there and the idea (for me) is to subscribe to them only. I don't find twitter invasive at all since all the activity occurs in the bottom corner of my browser; trick is to use the correct plugin/add-on to meet your needs.