From the "technical implementation" article they link to

>When you do a search on DuckDuckGo, depending on the particular search, we will make a call to Yahoo for links, ads and other content.

What would they power Yahoo with? DDG has always just shown Yahoo results (which in turn comes from Bing).

>DDG has always just shown Yahoo results //

Pretty sure that's not true. DDG used to do its own indexing IIRC. Early on in the project we used to get regular updates here.