I'm just back from the WOMMA conference entitled 'How Brands and Agencies can Master the Art of Word of Mouth'. The keynote speaker was Seth Godin of Unleashing the Idea Virus (and many more bestsellers). If you have not had the chance to see Seth speak, make sure you take the opportunity. He was inspiring, down-to-earth, approachable and insightful.
Panelists from the agency arena included Jonathan Carson from BuzzMetrics, Dan Balter from BzzAgent, Mark Hughes author of Buzzmarketing. And from the brand arena, Marc Sirkin (The Leukemia & Lymphoma Society), Jon Gabriel (Cold Stone Creamery), and Gaylene Nagel (Electronic Arts) presented extremely insightful case histories of word-of-mouth programs.
The case for wom has been made, very well, by this conference. In the meantime, all of the folks referenced above have published material that is well worth a read.