I like using Startpage as well. My concern has never been about sharing info as much as it relates to storing info. What they may be unwilling to share today may be compelled tomorrow through a variety of means. Anything stored on a server somewhere is free game and the volumes of info that could be compiled on almost anybody would stagger most people.
It says something about “Enhanced by Google.” What’s with that? It wants me to add it to Firefox? So it is some kind of screening or what?