It's extremely cumbersome and confusing to turn off. At first, it was opt-in. Once would ignore the notifications to turn things on, and eventually things became opt-out. But it's not 100% clear what one is opting out of - the only thing that seems you can really opt out of are ad-related tracking (by 'request' it seems - the ad tech companies get to use the honor system), and personalized recommendations. Well, just because you turn off recommendations doesn't mean they're not already collecting your personalized data - even if you don't use it.

Did I make mistakes in the above paragraph? Probably. But you know what, that's Google's fault, because it sure isn't clear what they aren't and are doing, who can and can't use it, and what I can can't opt out of.

That's the really frustrating part, here. It's purposely obfuscated and changing - similar to Facebook's privacy settings - to keep you on your toes even if you are in the tiny percentage of the population that actually cares. Most won't until something panicky / headliney happens to make them care. I'm kind of glad the EU is making life tough for American tech companies with regards to privacy (even though I work for American tech companies).

2-way personalized search. You search Google and Google searches you.

And the funny thing is that many of us don't even want personalized search.