Google has 59% of the US mobile advertising market

"Google garnered 59 percent of a U.S. mobile advertising market worth $877 million in 2010, thanks largely to the search ad business the company claimed was operating at a $1 billion run-rate this year.
Market researcher IDC said Apple was the runner-up at 8.4 percent of the U.S. ad spend, which rose 138 percent from the $368 million spent last year. Millennial Media collected 6.8 percent of revenue share for the year.
IDC analyst Karsten Weide added search and display ad revenues to calculate total market share. Weide, who factored in Google's $1 billion search ad run-rate, said Google's 2010 gross revenue will be $519 million. Apple will tally $73.5 million while Millennial will bank $60 million."
Source:  IDC data, reported by eWeek, 12th December 2010