According to its wikipedia article:
DuckDuckGo uses information from crowd-sourced sites (such as Wikipedia) to augment traditional results and improve relevance. The search engine policy emphasizes privacy and does not record user information. The company is based in Valley Forge, Pennsylvania.
Some of the code of DuckDuckGo is free software distributed at GitHub under Perl 5 license.
I thought I would do my part and give them a free plug.
So use DuckDuckGo.com !!