You do know that the "clientèle" that startpage caters to usually are involved in something they wish to not be found by authorities, right? Are you searching such explicitly illegal things that you do not want to leave a trail, or do you routinely search your own SSN?
FWIW, the search engine storage is only a part of the puzzle. There's a record on your computer, and a record of your IP address on every server you've ever visited unless you're using a proxy service, then you're either just way to paranoid or doing something illegal.