Blogger now allows people to use something called "Open ID". This means that you can log in to comment using any open ID, including Typekey and Wordpress. The Blogger website has more information.
I have now turned on the option that means you have to use an ID when commenting. You can still make one up, of course, but you have to give yourself a name and not just anonymous. It was always annoying to have four different anonymouses commenting on the same post.