Comment spam is a huge problem. No blog is safe. Some people have hopes in the rel=”nofollow” blocking the evil spammers.

The idea is that the search engine spiders will not index the pages
with the comments, therefore the links will not improve the link
popularity of these sites and remove the motivation. Hosted sites like
Xanga do not have nearly the volume of spam that I see at other sites.
I wonder if this is because:

1) hosted sites have developed superior methods to defeat the spammers,
2) 1,000 links from a host is not as valuable as a link from 1,000 hosts, or
3) something else I have not yet considered.