Brian Carroll points to an interesting article on b2b word of mouth marketing. Given the content, I might rename this article Interactivity gets people buzzing.
For a long time, folks have known that user groups, customer relationship management solutions, knowledge base systems- all contribute to word of mouth marketing. b2b interaction, like consumer marketing, is about building relationships and leveraging those customer experiences.
The Cisco Networking Community and Oracle Applications Community were early examples of company-customer/supporter interaction. You can read more about this here, in an oldie but goodie AdMarketing conversation on "How Marketers Use Interactive Tools".