Google versus comment spam

Google announced a technique for preventing comment spam. The idea is that by making the comment spam less valuable spammers loose the interest in misusing comments.

It works by adding rel="nofollow" attribute to hyperlinks. With this search engines can recognize untrusted links on a page, and use that information in their algorithms. Google says will use it in their ranking system, by not crediting the posted link.

It's a shame such measures must be taken, but I think this is a useful step against comment spam. I hope that when developers of blog software add support for this rel attribute they also include a way to remove the attribute if the comment is not spam. This will make 'good' links count in the search engines.
It gives site owners some new power, as they can decide who they consider good. But it's the same power we already have for blog posts, because each time you write something you decide which links you add.