I may be wrong, but I think that the parent of your post had a more limited idea of 'anonymous' here.
Your ISP knows all the things you say they do, but so far as I know, no ISP does the kind of social/networking stuff with your information that Facebook, Yahoo, Google and company do. A government agency can get information from your ISP, but your ISP doesn't "share" anything through default-to-yes things like Buzz. (I may be wrong about this. Some ISPs may do this too.)
You ISP is the least anonymous email provider available. They know exactly who you are, where you live, and can see everything you do online.