MediaPost reports that Apple is getting ready to announce a mobile advertising service (potentially called iAd) to Madison Avenue on April 7.

[It's been] described as "revolutionary" and "our next big thing" by Apple chief Steve Jobs, according to executives familiar with the plan.

Madison Avenue as a venue sounds more like an industry insider pre-briefing than a public coming out party, similar to how we heard big media companies were approached about the iPad before Apple did their keynote song and dance. If it is as expected, based on Apple's Quatro Wireless purchase and designed to give developers an easy, elegant way to monetize their iPhone, iPod touch, and iPad apps then we'd expect a more public presentation to follow -- iPhone 4.0 SDK Sneak Preview Event perhaps?

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And, of course, this would bring Apple fully into competition with Google and their recent AdMob acquisition. Much as Google's Android and Chrome OS-combo was a gut punch to Apple's core business, this uppercuts Google right in the mobile ad revenue choppers.

Hey, maybe that's what Steve Jobs wanted to tell Eric Schmidt yesterday over coffee...

[Thanks to everyone who sent this in!]