Search queries have different purposes. Personalization based on my preferences and past search works wonders for known-item seeking and for re-finding.

But for exploratory search and exhaustive search personalization works as an echo chamber (or filter bubble if you will) .

Then there is the problem of change and inertia. People change, their preferences vary in time. Personalization has an inertia that causes the recommendation engine to always be behind the actual preferences. It's more visible the better the recommendation engine.

I'm not saying personalization is problematic. There are problems with using it all the time and stealthily, without a clear possibility to turn it off.

It's not FUD, but a challenge to overcome.