I totally agree with you guys that forums still helps to improved SERP. I just get your comment on forums sig because in some forums that I've been posting really assure to me that forums sig is a waste of time it doesn't give any help when it comes to SERP and PR. Most of them totally disagree that forums sig still helps that's why I want to more comment on this from professional SEO because I don't believe on them.
It doesnt help for PR and SERP, i posted a 4 month experiment proving it. But its great for traffic, i know DP provides some users their highest single referer.