Personalized search has been available for some time, but on Feb. 2nd, Google ramped it up. As SEO Book repined:

In the past they typically placed a turn off personalized results whenever your results were personalized, but now they do not disclose when they are personalizing the results, so you don't know when they changed, which sucks.

Although the consumers were not stuck with personalized results, it was neither obvious that results were being personalized, nor how to deactivated them. As Search Engine Land explained on Feb. 2nd:

Starting today, anyone who signs-up for any Google service using a Google Account (such as Gmail, AdSense, Google Analytics among others) will automatically be enrolled into three additional Google products:

Search History

Personalized Search

Personalized Homepage

You can override the decision to have Search History enabled, but honestly, you'll need sharp eyes. I completely missed that this was added as a default choice to the new account sign-up page. In fact, I missed it twice, as I tested the system by making two different accounts.

The reason that Google has probably made deactivating the personalized search option so difficult is that they need to (1) justify the demand so that they can (2) gradually perfect the algorithm. Granted, this is scarcely an upfront way to go about. However, whether or not Google has something to gain from it, they obviously feel that personalized search enhances the user experience and is, therefore, the future of search.

If personalized search results are indeed the future of search, even though they threaten the SEO industry as it is currently known, it may not threaten its very existence. Reflecting on the issue from the standpoint of an average (re non SEO savvy) user, Gord Hotchkiss writes:

SEO is, and will continue to be, vitally important as long as organic search results continue to be important to the user. [...] But, organic optimization now has a completely new rule set, which will irritate the hell out of many organic optimizers.
[...]
Personalization is being implemented because it enhances the user experience. It doesn't take a "Rocket Scientist" (sorry, couldn't resist) to see that one set of search results is not the best way to serve millions of users.

[...] The days of the universal results page are numbered. Which means that the days of the reverse engineering approach to SEO are equally numbered.
[...]
Think of it as Public Relations on the Web. If you launch a PR campaign, you don't target a particular position on the front page of the NY Times, you target a type of audience.[...]

Now, SEO becomes the same thing. You don't target the first page of results on Google for a particular term. You target an end user.

What Hotchkiss' point seems to be hinting at is, just as there are advertising and marketing agencies that specialize in certain ranges of products and reaching certain kinds of audiences, there may be soon be similar SEOers. Basically, as a medium, the internet is still incredibly young, and as it matures, it's going to become a lot more segmented into niches than it has hitherto been. This is why Michael Gray seems to be missing the significance of his very own point when he writes:

I’m an intelligent human being and can make decisions for myself, and I don’t need search results treat me like I’m a child, thank you very much. Lastly if you were confident in the quality of your SERP’s you wouldn’t need to tailor them to me specifically.

Just as Gray is an intelligent consumer, so are other users out there. Essentially, consumers themselves will decide whether or not why want to use personalized search and, if so, whether they will be able to deactivate it right on the SERP or not. In a word, personalized search results are a incredibly new feature of a relatively young industry. The invisible hand will guide it toward its destiny over time.

Of course, Google will probably continue to be sneaky while it tries to figure out how personalized search should best be organized. However, they will also notice if they see users logging out a lot of the time. Similarly, them or a competitor may very well start offering a two colum SERP where personalized search results are on one side, and organic search results are on another. What is certain is that personalized search is here to stay, and SEOers would be better to start workign toward adapting to it and finding their niche in the new frontier, rather than losing any more time and wasting anymore energy holding out against something they cannot stop.