These days, no SEO means no website at all, as you won't get any traffic unless your advertise (both paying or mouth-to-mouth)
SEO is needed to get more traffic. I am sure that you cannot get more traffic via other ways(twitter,fb, hi5, group msgs and etc) than search engines. You will be able to get more traffic via search engines. So, to get traffic via search engines, you should do SEO. Without SEO, search engines will not that your site is there in the internet.
Of course SEO is important. It seems to be getting less important though as organic results are pushed further down by Local results and Pay Per Click
It is a must, (I don't think there are anyone who have all the confidence to say that his site don't need any SEO at all) don't doubt it, just work hard to do it better. Warm regards
I agree with Canonical and noam6767. SEO is not absolutely necessary for all sites. The site's purpose will be the deciding factor as to whether it requires SEO. As Canonical mentioned, sites that have never been SEO'd can rank in top positions for non-competitive keywords and phrases. Maybe even some could rank for competitive terms purely by luck. But since that fortune does not shine on most of us, SEO can be necessary for our sites. I believe SEO to be important for our sites, but I also deem pay-per-click to be absolutely necessary for our sites. For us, it's a combination of the two.