they count, just not much value. They hold about the same quality as a blog comment or a social bookmark. Power in numbers...
i have to disagree with Dan.. I am on page one for both Terms in my signature. of course I use those anchors in other locations but I am pretty sure DP helped.
I dont think it really helps. Google isnt stupid, it doesnt really add any value to the user. Also there are so many links coming from DP that a forum link wont do much.
Can you prove it though? Are you willing to remove the DP links for say... six weeks... and see what the results are?
Well bro, A suggestion go on seobook.com and install an SEO add-on on ur mozilla browser and SEO quake. They will tell u which 1 is do-follow and which 1 is no-follow. U can easily use them to build backlinks for ur site.
DP doesn't nofollow the links posted on it. But as someone stated before there is power in numbers. If you take part in 15000 threads ie have 15000 posts it will be better than having 10 posts with your link. Your signature will show up alot more often and therefore have alot more backlinks but due to recent changes, Shawn is updating the signature system so it could change later on. (PS I'm not suggesting going around and posting your site's link in 15000 posts as it was merely an example)
Speaking from personal experience, not even having 15,000 posts will have much of an impact on your rankings.
I agree wth what most others have said in that it does help, but only a very small amount. Yes, I'm sure that having 10,000 posts is going to be better than 10 posts, but it's never going to be enough to get you to number one for a competitive keyword. Personally I enjoy spending time on forums, so if I get some benefit form the sig links then I see it as a free bonus. I think the worst thing for both yourself and the forum is to go making hundreds of posts just because you want the links - your time is much better spent elsewhere. Just enjoy the forum, thats what I do.