I'm not sure . . . If there is a no-follow setting on a link the page rank giving is only the blocked from your site to the link, but the spammers can get a good position in the search engines by the spam keywords.
Originally Posted by mokmok69
Just for a sample:
If the owner of Spam Page has many links on different blogs' comment pages according to the above HTML code, he or she can get a very good position in the search engines with the "Spam Page" keywords. And you know for the good business not the value of Page Rank is the important, rather the relevant site traffic must be in the focus. That's the reason why the viagra can be a good online business and in the top most cases the owners are spammers!
<a href="http://www.pageofspammer.com" rel="nofollow">Spam Page</a>
According to my opinion the "no-follow" setting on a link is not enough protection. On the comment places the captcha solutions are really useful and of course the best if the comments are editable by you. On WordPress it's possible and the Akismet plugin is really great for the catching of spams!