Google shows this forum as a back linking source from my sites and also getting some visitors but that not so significant in terms of volume
I do not know anything about this, because I do not own any website, lol... I usually believe in selling my sign, but now I came to know why people pay for buying other's signatures.
Based on my own experience I can tell you for a fact that the signature links here at dp has helped many of my sub-pages to rank very well in the serps.
The SEO value is really low, sure, if you have 10k links here it may help a bit, but if you are posting to get links you really waste your time since there are other things you could do at the same time that are 100x as effective.
OK. I finished my research. It is far from scientific. Basically, I found 12 pages on my site of 500 pages which had some original content and which should have some links but instead, google was showing NO external or internal links for them. I interpreted this as meaning that they were in the supplementary index. I tried various strategies on these pages. One for instance, I put in my signature on this forum and then posted a buncho times. Two weeks later: the page with the links from this site was NOT one of the ones that Google showed with external links. The entire results can be found at: learn-to-market-online116.blogspot.com/2009/01/supplementary-index-research-analysis.html I'd be very interested in other research of this kind or any informed opinions on the methodology. Obviously, I"d like to perform the test half a dozen times on different sites with different variables to see if the results are random or consistent.
Signature links here do have value. I suggest you target pages away from your index page though. DP passes on some link value but not enough to get you up to the 'big keyword' which many people target with their domain/index page. I have used it in the past to rank top for terms which are not so popular but are popular enough to bring in traffic. Commonly on subpages. I find the effect of the links from DP have a bigger effect upon subpages than my index page which already has high value links. This resulting in a bigger gain of traffic. I explain this above however it ultimately depends on your site and your structure. Experiment there is very little to lose as you will learn from posting around this forum too.
I haven't explicitly tested Google's handling of signature links from DP, but I have discovered how they handle them in another forum I use frequently that is also based on vBulletin. My information isn't absolutely conclusive, but it is pretty strong evidence that Google filters signature links when they can. I noticed that the Links tool in the Webmaster Tools console showed links to some of my pages that were coming from messages I'd posted. But absolutely none of my signature links in those same messages were being reported. That is, Google was able to distinguish between links embedded within the message text and the signature links. It would take much more testing to be really conclusive, but it does seem to me that Google is discounting signature links when it can. There could be a difference in the way DP has configured vBulliten that makes it hard for Google, but I doubt it. Has anyone seen a signature link appear in the Links report in the Webmaster Tools console recently? As an FYI, I do see indications that signature links here do help some in Yahoo!. Nothing in MSN.
In another forum i go too, about 6 months (or maybe more) ago Google Webmaster Tools counted thousands of text links from a signature on a phpbb forum i go to. But recently, a few months ago, i believe most, if not all, of these text links dissapeared from google webmaster tools. So i think Google may have a way of finding out... although its probably far from perfect.
Google highly devalues signature links, but they're helpful for yahoo, msn and also for traffic you get from the signatures.
I practically knows sites can get top serp positions only from forum signatures links. Even we forget SEO benefit still forum signatures can bring lot of referral traffic.
I would imagine Google crawl DP at least once a day if not more so the links must have some effect on your visibility to Google, but don't links on pages with lots of link have less weight towards PR than if yours was the only link on a page. Also, it would be worrying for me as a newbie if people were joining DP, not to give me (and others like me) advice but to simply boost their own PR!