"You can't know that anything (especially on the server side) is actually
private."
That's just it...
Unless it's a service managed by someone you (personally) know good enough or
know that you can trust in, as long as there are governments and corporations
out there wanting to violate your privacy, you can *never* be sure you can
believe the "privacy statements" this corporations present to you.
Concerning the apparent good intentions and reputation, among the privacy
community, that this "Startpage" project has built...
Read a book, that Richard Stallman sometimes mentions in his lectures, called
"Nineteen Eighty-Four".
It's a book that was written by someone who worked for the same interests I
was talking about, and a description of what was planned (at the time it was
written) for the society we nowadays have - and also one that describes, very
well, much of what we are already witnessing.
In that book, the main character also finds out about an organization that he
thought was fighting the people who controlled the society he lived in - only
to later find out that the whole organization was actually a trap, designed
to catch people not going along with "herd"...
That part of the story is an allegory for the construction of all sorts of
different (fake) social movements (like many that we nowadays have) that are
actually controlled by (and working for) the powers-that-be.
"The best way to control the opposition is to lead it ourselves."
--- Vladimir Ilyich Lenin