Here's just one example how comment spam is making the blogging world a crappier place (warning: clicking on the following link may cause your browser to jack your computer's CPU to 100% for several seconds): http://dotnetjunkies.com/WebLog/jonne%20kats/archive/2004/01/14/5589.aspx
This link is a blog entry from Jonne Kats asking the blog community if there exists an easy-to-use control for WYSIWYG editing in a WinForms application. I was in search of such a component earlier today and ran across this blog entry, but upon trying to visit the page, my CPU's utilization jumped up to 100% and my browser hung. After a couple seconds of waiting, I restarted my browser and tried again. This time I had more patience and, eventually, the page was rendered.
The reason it took so long to grab was because the page was over 3 MBs of HTML, with apparently hundreds of comments, as the little scroll bar was tiny, indicating that the vertical length of the page was huge. Upon scrolling through the entry, I found that there were about five “real” comments at the top. The rest - several MBs, I'd imagine - were nothing but comment spam. Ick.