For all you spammers out there

[NickFitz]

You have to make the links from the forum nofollow.

You will just get picked on by spammers until you do that.

Linkspammers couldn't care less. Adding rel="nofollow" attributes to links prevents their links gaining Googlejuice, but it's never discouraged them from posting the links and it never will. They don't bother analysing sites to determine which do and don't use nofollow; they just post their tulipe everywhere. It costs them nothing extra, and filtering would cost them more.

In the linkspam economy it simply isn't worth going to the trouble of filtering out a million places that use nofollow so as to be left with the 190 million that don't. They just spam the lot. Spamming has always been a scattergun approach. All nofollow does is protect one's own PageRank from the consequences of spam, but it does nothing to prevent spam being posted in the first place. If you want evidence, set up a WordPress blog and see how many spam links you get in the comments, all of which are nofollowed.