If you are posting in forums directly related to your niche, and your posts are extremely good and offer unique information, then you might manage to drive some traffic. If you’re going to be doing things like so many people do here where they say “hi guys, I think google is important to SEO, please visit my website” then you will definitely be wasting your time.
http://forums.seochat.com/google-optimization-7/what-are-your-thoughts-on-forum-posting-279543.html#post746583
The main reason people like the concept of forming an SEO Monopoly is leverage. Traditional SEO is like putting all of your eggs into one basket. An SEO Monopoly is equivalent to owning multiple baskets. The odds of a the searcher finding out about your company or service are much greater if you are running an SEO Monopoly.
