As has been widely reported, Google has implemented a nice hack to blunt the comment and referal spammers that have become the bane of bloggers lives of late. The Register however, has an interesting take on the new tag, claiming hysterically:
But all these may look like an innocent prelude. Google said today that its search engine will respect a new link attribute, “rel=nofollow”, which will means its algorithms will not give weighting to the target URL. MSN, Yahoo! and blog vendors said they’ll follow suit. It’s effectively declaring PageRank? dead for weblogs, in an attempt to stem the problem.
Utter bollocks. Total, unadulterated bollocks. Someone at el Reg needs to be smacked with a cluestick. The “rel=nofollow” tag is totally optional, and in the case of most blogs, will only be applied to links within comments on articles. The interlinking of blogs typically comes about from one blogger posting an article with a link to another article (so in this example my link to The Register above does not have the nofollow tag). Google does not propose that all article links apply the nofollow tag. That would be idiocy.
As far as I can tell, there is no harm in not PageRank-ing comment links. If I want to comment on another blog, and want to include a link that I think is important, I’ll make a new article on my own blog and link (without the nofollow of course) to the original. Of course if I’m just providing extra info via a comment, I see no harm in the target of my comment-link not receiving PageRank.
I think of it as an extension of robots.txt to the individual link level, rather than file-level.