Neil posted a suggestion on how to ebb the tide of comment spam. He suggested that you stop search engines from indexing your blog comments. The theory is that (if the links posted in/by comments aren't indexed in the search engines, then A) it will be harder for spammers to find you site by searching for spam links in Google, and B) the spammers won't have much of an incentive to post comments to your blog.
This is sound, in principle, but I think it would fail in real-world application, because, A) this method doesn't do anything to offset all the comment links that are already posted in the search engines. I suppose you could go through and ask all of the search engines to delist your pages, but that seems extreme to me, and, B) if someone is going to spam your blog comments, are they really going to take the time to read some disclaimer that links are not enabled? I really doubt it. Then you're left with a blog full of p*nis spam sans links. I mean, great – no links. But – the p*nis spam is still there, right?
The whole point of cutting back the comment spam is to get rid of all the extraneous, junk comments. Having p*nis comments without the links just doesn't cut it for me. I don't want any extraneous comments. None. Zero.
In my opinion, there is only one way to cut back on comment spam and that's by using Jay Allen's MT-Blacklist plugin.