incrediBILL - 4:54 am on Nov 7, 2010 (gmt 0)
We personally nofollow ALL links on our forum
I don't nofollow them just because nofollow is a farce.
I encode the URLs and send them thru a redirector that decodes them and I block all SE's from following links thru the redirector, which also avoids 302 hijacking some site by accident.
That way I'm 100% sure they never get credit for the link and I also get a 100% accurate click thru count for all links on the site ;)