Snap.com has an interesting new search engine out. I think it might be a little too clogged with information for the average user, however, I think it also poses some interesting views into the direction that search engines may be headed. According to Snap, it uses traditional search engine methods plus post-query click-stream data to determine the Snap Rank, which is the order in which Snap displays results...By knowing the Web sites that users spend time on and the sites they quickly leave, Snap Rank provides higher quality results than pure algorithmic ranking.
As I mentioned, the results interface is interesting but probably overload for the average searcher. Still, if the methodology behind the SERPs catches on with the bigger search engines, it could change the landscape of SEO significantly. Like personalized search, this kind of ranking takes a fair amount of control out of the hands of the SEO. Suddenly, content DOES become more important, as user feedback and their choices become more important in ranking. This, of course, could go a long way in eliminating spam results, which actually might lead to easier optimization of a real, content-rich website.
As always, interesting times ahead for the future of SEO.