It's been more than a year now since you're writing anti-google and anti-personalized results articles. It's getting old and people love personalized results. I don't think it should be made opt-in as I think Google (and any product) should make the best option opted-in by default, and personalized results is the best option as it offers the best experience for regular users. Why would they offer a worst experience by default? It doesn't make sense. Also, most people don't know or care enough about changing options so they'd just keep the worst experience by default.
Let's take my brother's example again, if he searched for "ruby" and got results about rails and ruby.rb first before the gemstone because they are more popular than ruby the gemstone, my brother would just be confused and may even waste time clicking on the rails link first. So what should google do, propose a link that would say "opt-in to have search results that actually make sense to you". Do you see how absurd and bad UX that would be?
People who care about these kinds of things already opted-out, in fact, the most paranoid hackers I know don't even use DDG, they use Google+Thor and turn JS/cookies off. It's cool that DDG is adding more features but that's not anything I care enough to use or I could just write a quick google chrome script that'd do the same.
it seems to me that both google and ddg have problems here, ddg in not personalising at all, and google in personalising things that really shouldn't be.
I think DDG has some personalization based on your location, for example if I search "weather" it shows me the weather near me.