I've been getting a new type of comment spam on my other blog. The spam is a statement that is very coherent and totally relevant to the post, but then at the end has a link to a page that is filled with a huge list of links to other pages on the site - all for the sake of trackbacks. My guess is that they are copying text from other blogposts, then googling for related blog posts then pasting the other blog's text along with their own link into the comments.