Move over, AdMob and Millennial. Apple CEO Steve Jobs presented a slide at this morning’s Worldwide Developer Conference in San Francisco that claims that 48% of spending on mobile advertising in the United States from July through December of 2010 will go to Apple’s iAd advertising system for its iPhone and iPad portable gadgets.

“We’ve got advertisers committing to sixty million dollars,” Jobs told the assembled crowd of software developers and journalist. Among the committed advertisers, Job said, are Nissan, Citi, Unilever, AT&T, Chanel, GE, Liberty Mutual, State Farm, Geico, Campbells, Sears, JC Penny, Target, Best Buy, Direct TV, TBS, and Disney.

What iAd offers advertisers is guaranteed reach across a wide audience. That’s why big brand advertisers are signing up. So far, Apple hasn’t demonstrated that iAd will have the sort of personalized “long tail” targeting that made Google’s AdWords and AdSense a multi-billion-dollar business.

Mobile advertising experts and Apple’s competitors haven’t weighed in yet — Steve Jobs is still onstage as I type — but their counterpoints to Jobs bullish claims will be interesting.

[Photo courtesy of Engadget]#mce_temp_url#