To get back to the original topic: Do search engines pick up and index only some signature links? (Of course we know that some forums block the search engines, so we know they won't get indexed) If so, what links get indexed and which don't? Of the links that get indexed, which are most valuable?
Sig links ..rock ..just get a busy little poster and you see a lot of return. Big money IS not the important part with these links the activity daily is what helps..in some cases it even blocks some of your compitition as well.. lol
Google crawls active forums very frequently. This is because active forums change very fast and they want to capture it. For example DP, NP etc. This makes the signature links of frequent forum posters very useful to get crawled.
There's a reason why this forum forces at least 10 posts before allowing links in signatures. If they didn't people would simply flood the forum with links to get better rankings! Forums want quality posts which in turn makes the content on the forum more targeted. This is good for those who are eventually allowed to include links because their links will be surrounded by 'real' poster content and not just spammers' links.
Do you believe that the sig links give relevant traffic? but if i have a link here - in dp- , for my celeb site, will it bring traffic who will really search for celebs?
Sig links generate good traffic for many reasons. It all depends on the keywords you use on your sig.