I could be thinking naively about this, but it will be interesting, if it happens, to see how Google stands up a successful mobile ad market.
While the main motivation for wireless technology and mobile devices is convenience and mobility, folks are also interested in accessing the Internet without the "Internet junk" that comes along with traditional desktop web access. Sure--everyone likes restaurant finders, turn-by-turn navigation, and voice-activated technology, but those apps are built specifically for mobile devices and are convenient.
I just donít think users will buy into apps with ads. I think getting users to engage in PPC-type mobile ads will be difficult. I think the lack of "in-your-face advertising" is part of the beauty users see in the mobile web.
With iPhone and other devices, for example, you can tie web-based mail (POP, IMAP) into your phone settings which allows you to retrieve/send messages without dealing with the Flash-based, 720x90 ads across your screen. You typically get the same ad-less interfaces with other mobile applications such too. And let's face it--most folks looking for convenience in the mobile arena see "convenience" as being able to get to easily post to their social networking sites, or locate a trendy cafe, or upload a 5-second old photo.