"DuckDuckGo gets its results from over 50 sources, including DuckDuckBot (our own crawler), crowd-sourced sites (in our own index), Yahoo! BOSS, embed.ly, WolframAlpha, EntireWeb, Bing & Blekko. For any given search, there is usually a vertical search engine out there that does a better job at answering it than a general search engine. Our long-term goal is to get you information from that best source, ideally in instant answer form."

source: http://help.duckduckgo.com/customer/portal/articles/216399-s...

Yeah, DDG uses Bing as one of it's sources. It's similar to the "meta search engines" of ye olden days.

DDG's big schtick (other than privacy) is to use lots of sources and then heavily filter the results/supplement them with additional sources (wiki, stack overflow, etc).

The founder of DDG has said he specifically wants to avoid writing a general-purpose spidering engine because you can sink millions of dollars into it and still be miles behind the competition.

No, there are over 50 sources: http://help.duckduckgo.com/customer/portal/articles/216399-s... And they aren't just copied verbatim (with the same ranking, etc), but are re-ranked and mixed.