I am all for the nofollow. I guess some people feel it necessary to spam every blog they can. But my philosophy is if you are spamming my blog then you really must be hard up for hits to your website. So I make it a point not to even click on the links supplied in my blogs comments section. I also tell people never to click on these links because you never know what is on their pages. You might be selling something, and you could be downloading something else onto my computer behind my back. Or you could be advertising one thing, and selling a entirely different item on the website. I tell all visitors to my blogs:
Please don't click on any links in the comments section of my blog. You never know what could be lurking at these websites. So for your protection, dont visit these websites.
Here is Googles info on this subject: