I don’t say that SEO is not useful. I support my pages with heavy SEO and accessibility methods – What is good for the user, will be very good for SEs too.
But for me relying only on Search Engines is scary. “Don’t put all your eggs in one basket.” It is like you promote only one brand… What if that brand will go bankrupt?
Search Engines are important. But trying to diverse your traffic inflow is a must. Good example: we don’t know anything about how search engines will handle the new TLDs… What if they will prioritize .gambling, .poker etc TLDs?
I just say that have your traffic from the SEs, but diversify to another traffic sources too (bookmarks, forums, sent out newsletters to your readers, gambling blogs etc).