Most people don't realize this, but DDG doesn't sell their own advertising, they use Microsoft's advertising network! This just seems bizarre to me that they're outsourcing the whole reason they're supposed to be independent of the other search engines.
I tried signing up for Microsoft's network, but it was a bad user interface (typical MS), very confusing, and I couldn't really figure out how to specifically target DDG and only DDG. I just gave up.
DDG needs to bring advertising in-house, or I don't see why they have a reason to exist. They're almost a subsidiary of MS at this point.