Talk to some online marketers and SEO is everything. Talk to others and they know nothing about it. My philosophy is somewhere in the middle.
I think SEO is important. It isn't everything, but it is important.
Let's look at domain names, for instance. Many successful online companies have built solid brands without keyword-based domain names. Google, Yahoo!, Amazon, Bing, eBay, Facebook ... just to name a few. Have you noticed that all of these companies are in the top 10 most trafficked websites online? Facebook is No. 1 and Google is No. 2.
That's not to say that these websites aren't SEOd. They have certainly considered SEO in their overall marketing plan online, but they don't put SEO as the point to emphasize against all other points. There is something to be said for branding as well.
When you build your online presence, think about SEO, but don't think about just SEO. Think about your overall marketing goals and how SEO can fit into that.