Thursday, October 13, 2011 at 5:07 pm.

Google mobile ads now a $2.5 billion run rate business

Google CEO Larry Page just said on the company’s earnings call that Google’s mobile ad business is now on a $2.5 billion revenue run rate, up from $1 billion a year ago.

In the context of Google’s overall business, that’s still pretty small — well less than 10% of Google’s revenue. But expect it to keep growing rapidly as smartphone penetration — and therefore mobile search and display ad revenue — keeps expanding.

(The challenge to this would be if a company like Apple disintermediates Google in mobile search. But that probably won’t affect Google in the near-term — especially as Android continues to grow.)

Google declined to specify what percent of its mobile ad revenue was search versus display.

Related: Watch as Apple’s Siri starts to remove Google from the mobile search equation