First, I don't work on Search, I work on open-source stuff, and this is just my private opinion.
Secondly, I am for the idea in theory, I just don't think it is practical to do in a way that adds a lot of value. You also have to worry about the legal/privacy ramifications of funneling everyone's queries out to third party providers, I'm pretty sure that would cause a large blowup.
Third, there were already services that sort of did what you ask, for example, MetaCrawler, which was around way before DDG, would federate out queries to multiple search engines and combine the results. It wasn't very pretty.
I'm not sure IFRAMEd results really add that much value for a user, but one could easily conduct the experiment by making a Chrome/Firefox extension that replaces Google Maps results with OpenMaps.
In an ideal world, one wouldn't need fleets of cars and people to make maps databases. There's be some kind of standard, like http://acme.org/geo.json or maybe KML where crawlers would crawl the web to get accurate business listings, indoor maps, photos, menus, hours of operation, and other stuff. And then anyone could write a little bit of JS that could be registered with the browser like <link rel="geopanel" href="geopanel-fancy.js" type="application/business-data">, and when Google or Bing when to show a business listing, they'd just need to output the json record, and any registered providers could render it.
I'd be all in favor of a fully federated world, I'd spoken about it at length in the past (http://timepedia.blogspot.com/2008/05/decentralizing-web.htm...)
But I think one has to be realistic that the the fully open, federated solutions often do not compete favorably with vertically integrated solutions from a user experience point of view. They often can only do so once the underlying features have been fully commoditized.