Google's method to fight comment spam

 From what I gather comment spam hasn't been much of an issue in Xaraya 
yet, but it's something to keep one's eye on.

Google has a proposal that is backed by a few other systems to help 
fight comment spam by skipping links in comments that have a 
rel="nofollow" tag appended to them.

You can read more on it here 
http://www.google.com/googleblog/2005/01/preventing-comment-spam.html

-cwolf