There is a wonderful thread at Cre8asite Forums that has a theory that SEO is always not necessary or required. He gives several examples, each example can be argued with, but that is what makes it fun.
The problem I think is the underlining definition of what search engine optimization (SEO) is.
Does this site require SEO? Heck, I have not changed the the site in ages, all I do is add content. Is adding content considered SEO? Is the style of how I write make my content SEO'ed content? Since my content tends to attract a couple links per article, does that make it SEO'ed?
Here are the examples given in the thread for when SEO is not required:
1. If your website is very specific for certain group of audience and does not require too much of public intervention then yes u do not require SEO. e.g. sites of universities and organizations especially made for students and employees resp.
2. When ur site already ranking well in the search engines, due to brand name etc, and you're satisfied with the traffic n sales the u don't require SEO.
3. When you facing some business fallouts, then u need to concentrate ur resources n energy elsewhere rather than SEO.
4.If you are planning to revamp or redesign your whole site again then go for SEO only after you have restructured your site again.
EGOL, moderator, quickly gave objections to each one and they are valid arguments.
As I scroll down the thread, softplus hits it on the nail.
Of course the larger question is: what is SEO?
I think that is the root issue with the thread.
Forum discussion at Cre8asite Forums.