Advertising on mobile phones will take off when users believe they can control them.

Mobile Marketer: Traditional advertisers ramping up their mobile strategies: Study, 2009-Jul-17, with Giselle Tsirulnik interviewing Mack McKelvey of Millennial Media:

“Entertainment advertisers … know the power of the mobile ad network model and they strategically leverage it to target and engage their consumers with unique interactions at various points in their campaigns.”