With all of the silly people buying into the personal search by staying logged in to their Google.com accounts the future of traditional
SEO is going to become more PPC focused. At this point the only way you are going to be able to guarantee placement within all of the different personalized SERPS is through PPC.
This is fine for sites that can afford PPC but what about the sites that can't, what are they going to do? Personally I think that the search engines will offer another kind of paid inclusion, one that will by pass personalization settings. In doing so the search engines will open another revenue stream from the same customer base.
Personalization allows the search engines to put even more emphasis on PPC but while that might be good for their bottom lines it could also make search engines like Google a little less reliable.
Case in point, I can not count how many times I have referred a friend to a site by telling them just to Google a specific term and look for the listing with the domain of whatever.com. Now seeing as these conversation happen over the phone it is just easier than say reading out a really long database generated, operator filled URL. This worked in the past because the SERPS were generally pretty close regardless of where both parties are located.
With personalization in place this may no longer be a convenient way to communicate web finds with friends, family and clients. Well not convenient to do it with Google say.
Another example of how personalization hurts the over all searcher experience, new sites might not be as likely to show up in your personalized results. By the time you have filtered out all of the sites you are no longer interested in by voting them down or by voting up all the old standbys, new sites will have little success in penetrating your fave 10 unless of course their is some kind of search engine intervention.
Now I don't know about you but one of the reasons I use search engines is to find new sites and content and if I can't get the new stuff because all of the personalized search results are potentially influencing organic rankings, well I just won't continue using that search engine.
The future of
SEO as we know it now, will be severely undermined and devalued by personalized search.
SEO will move more into SEM and usability fields. This is a genius move by the search engines as it removes potential problems with spam infiltrated SERPS and it puts even more emphasis on PPC. I seem to recall some search engine stating that they would do no evil but they never said they wouldn't use evil genius.
So remember all you worried
SEO people, stay logged into your Google.com accounts at all times so you can help the search giant put you of work.