[Okay, turning your prospects' cell phones into ringing spam machines is probably not your idea of cultivating goodwill. And it's not likely to happen. Unlike e-mail, mobile phones aren't readily accessible to marketers -- mobile phone privacy is zealously guarded by big carriers like Verizon and Nextel, as well as by law. There's an opening, however, and smart advertisers are preparing to drive a truck through it. Provided a consumer clearly opts in -- say, by dialing or text-messaging a certain number -- carriers are slowly becoming more or less amenable to letting marketers return a text message, or even an audio or video file, to that consumer's phone. Mobile phone ads are already big in some parts of Europe and Asia, and it's just starting to take hold here. McDonald's and Dunkin' Donuts are among the companies that have beamed coupons to U.S. cell phones, eliciting coupon-redemption rates as high as 17%.] Mobile-phone marketing today is where Internet advertising was in 1996 -- it's about to take off, ... There are already more mobile phones in use worldwide than televisions and computers put together.
— Michael Baker
GoodwillMachines