After yesterday's excitement, this sort of thing just upsets me more: you too can make the world just a little worse for just $19.99. Via Darren Rowse (I won't link to the SEO twerps directly), we find this:

Blog comments help your site rank better in the SERPs. We hired a few people who go through a list of blogs in a database we set up and pick out blogs that are in your niche. They then read through blog posts and leave a comment that has to do with the blog post they read, that way it wont get deleted. Your backlink will then be on a targeted blog, giving you more weight in the search engines.

This is how you end up with "related" comments that say "great site, thanks for the information" - and then link over to pharmaceuticals. I think Glenn Reynolds has the proper level of contempt for these guys.