Also annoying are people who post 10 tweets in a row, especially if the tweets are not of general interest. These people are usually the same ones who tweet 50+ times a day.

I think people who post the kinds of statuses you discuss, as well as the overtweeters, think of social media as a way to vent or communicate with select individuals. They're not focusing on the fact that all of their followers can see their updates. It's a very self-focused, as opposed to audience-focused, approach. Which is not always wrong, but can be aggravating.