Well, even though I agree with you, I must point out which in my opinion is the greatest reason why DN has collapsed: personal agendas, lack of altruism. The truth is people post and comment when they want something in exchange: in most cases attention on their work, projects, and whatnot. People don't interact for the sake of a better, more comprehensive community, that's a mere utopia. People do it so they can leverage a group of other people. Truth be told, it is a matter of mentality which will hardly change – Dribbble is exactly the same.