I've had to turn anonymous commenting off. I just received four spam comments within two minutes and that's pretty much the last straw for me. I have been getting multiple notifications a day about spam comments, all anonymous, and it's just got to be too much. Blogger is very good at identifying them as spam, so they never get published but the constant email notifications are tiresome.
So. From now on, if you want to comment, you will no longer be able to do so anonymously. I'm sorry to the legitimate commenters this will affect but I hope you won't let it stop you from leaving a comment if you'd like to. It doesn't take long to sign up for a Blogger or Wordpress account (these are probably the two easiest ways of commenting) and there's no reason you actually have to use the blog for anything. I have a Wordpress blog I only ever use for commenting. :)
Once again though, I'm sorry for any inconvenience this might cause. Blame the spammers. ;)