Not that this will necessarily come as a surprise to you, but it seems pretty obvious that Google is powering Ask's organic search results. Ask has an open partnership with Google for its sponsored search results, but will not come right out and say who is powering its regular results.
I'm not sure that there was much doubt it was Google anyway, but after looking at Google's results for "viagra" in light of its Penguin update, and comparing them to the results on other search engines, Ask's SERP for the query was nearly identical, down to the specific flaws we pointed out about Google's version. Google has corrected some of these flaws, and those same ones appear to have been corrected on Ask's version as well.
A spokesperson for Ask told us, "A third-party partner powers core web search on Ask.com, but that information is not public for contractual reasons."
"Ask’s search technology is focused on surfacing answers to questions rather than links, and it’s powered by a combination of technologies," she said. "A third party search engine supplies the raw search feeds and we build our own algorithms on top of that, designed specifically to locate and extract answers to questions."
Here's what Ask says on its Editorial Guidelines page about its automated search results:
Ask.com delivers its primary search results using it's proprietary search technology. These search results appear under the heading "Web Results". Ask.com search technology uses sophisticated algorithms and Subject-Specific PopularitySM data to generate the most relevant and authoritative results on the Web.
Here's what it says about its sponsored links:
Results appearing under the heading "Sponsored Web Results" or "Sponsored Web Result" are provided by Google, a third party provider of pay for performance search listings. Google generates highly relevant sponsored results by allowing advertisers to bid for placement in this area based on relevant keywords. These results, which are powered by Google's advanced algorithms, are then distributed across the Internet to some of the world's most popular and well-known Web sites, including Ask.
Here's a screen cap of the "viagra" results before they were fixed:
You can just compare the results to the ones I talked about in this article and see the obvious similarities (which were not all duplicated on the other search engines).
By the way, if you ask Ask.com, "Does Google power Ask.com's search results?" the top two results are articles that suggest that Google may power Ask.com's search results. Of course, they also happen to be the same results Google gives you when you ask the same question in a Google query.
If you're counting Bing and Yahoo together in those search market reports, you might as well be counting Google and Ask together as well. And AOL, of course.