Google is working very in the mobile ads business. And in the patent application too. Its start by (sort by date of the filed demand)
Method and system to provide advertisements based on wireless access points and then 3 months later a Method and apparatus for customizing travel directions and this new one for Visually-oriented driving directions in digital mapping system last summer. Lately, it was that small addition to the robots.txt.
Via Rusty, William and Michel.