I would say that forums are place of learning and earning too. At the same time you would be earning while learning it is true, and you would get practical experience if you participate in forums. For learning SEO, it is really good place, as you are able to share your knowledge, other experienced people would also share their knowledge, experience, tips, tricks, you are able to put any question and it would be answered shortly.
I agree with you, I offer SEO services and web development services. I have recently got 4 SEO projects from a USA based client and I think he came to me in contact from a forum. I agree with you that you can not only learn via forums but Allah can make you to earn money via the Forums as well.