I think there are other reasons as well (e.g. analytics, as mentioned in the post, when links are consumed through third party clients), but I don't buy this on

I think there are other reasons as well (e.g. analytics, as mentioned in the post, when links are consumed through third party clients), but I don't buy this one. Wouldn't this only be useful in breaking spam links when they are spread beyond Twitter? On Twitter itself, they don't need a URL shortener, they just need to remove the offending tweets. It might be a nice side effect, but I doubt it's the real motivation for shortening everything.