I don't mean to say that you shouldn't be doing PR, Marketing and Social Media efforts; because you should. Yet, I don't think of press releases, making awesome products and participating on social networks to be SEO. But if you do them right, you'll get link backs as well.
Too many posts about SEO get everyone obsessing over marginal website tweaks/details when a single backlink to their webite doesn't even exist outside of their HN account.