Blog spam, WTF?

I just got blog spammed! Essentially some !@#$ posted a generic comment with a link to an advertisement page. WTF? Is this common. I guess that's why you have the option to only allow registered users to post.

Update: I just saw another friends blog with a spam post, this one even more obnoxious, and from a registered user. (Most likely a bot registration, the blog was empty) This could suddenly become a problem, but hopefully the guys at google are smart enough to figure it out shortly.