Lets say I have a dog food niche, and I join a dog food forum I post about dog food, and at the end (in my sig) I have a link to my website with anchor text. Do I get a nice link with EACH post that I do? Or does google look and just count mainly *1* link from that site? If google looks at it as multiple links, they're devalued, correct? since they come from the same place?
Yes you would get 1,000 backlinks from that domain if all pages you post on are indexed. No one knows exactly but many say if you have 1,000 links on one domain such as a forum that most of your links will decrease in value because Google knows what is going on and that it is a sig. Either way I have seen a good boost from forums not as far as traffic because it is little but in SEO value.
You should build as many backlinks as you can from do follow forums even though dp is completely unrelated to my site I have received quite a boost in the serps from my backlinks here at dp.