[1] indicates DDG uses third-party APIs for deep web searches. To me that sounds like how Inktomi was a "search engine API" and neither Inktomi nor Yahoo saw Google coming [2].
Even if DDG doesn't succeed, Google is now at the top of the hill and therefore is _the_ target for all competitors.
[1] http://help.duckduckgo.com/customer/portal/articles/216399-s...
[2] http://diegobasch.com/a-relevant-tale-how-google-killed-inkt... and HN discussion http://news.ycombinator.com/item?id=3924609