I had been following 18 or so twitter users, most of them theoreticians and including the very useful @cstheory feed, by using an RSS feed to integrate them into a stream of 150 or so different frequently-updated web sites that I keep up with through an RSS newsreader. But more recently, twitter has cut off RSS, and has made it only possible to access twitter through their own site or their own apps. (Actually, they made steps towards cutting off RSS over a year ago, but I had been working around that and now the workaround has been cut off too.)
This sort of behavior is not acceptable to me. I do not want to have separate applications or separate bookmarks that I have to check for the updates on each of twitter, tumblr, youtube, blogspot, wordpress, etc. that I wish to follow; I want as many of them as possible in one place. That is exactly what RSS/Atom are for. And, the low signal-to-noise ratio of a lot of the content on twitter (sorry, but it's just not possible to go into much depth in 140 characters, and much of the content there simply provides alternative links to stuff I'd already found elsewhere) means that it's not important enough to me to find an alternative way to read it.
So goodbye, @cstheory, and all the other theory twitterers, and goodbye, twitter.
ETA: False alarm. Twitter is still phasing out rss feeds, and I still think that's a bad thing, but there are still feed urls (different than the ones I had been using) that work for now.