A lot has been made of Twitter use by larger companies to interact directly with customers, sometimes more quickly and effectively than with more traditional customer service tools, such as telephone, email or even letters. Twitter has made it possible to get real time information out to customers much more quickly. And customers have used it in the other direction, to send immediate feedback to companies.
While much as been made of the Comcast & Whole Food models, smaller companies are using Twitter in very inventive ways, that actually don't just benefit their marketing profile, but benefit their bottom line. An article in the New York Times, discusses some real world examples.