Ask HN: Social Networks and Business?

I managed to impress a manager at a local Fortune 500 company during a class we had at the local chamber of commerce - to the point where he asked me to stop by his shiny new office and give him a run down of how businesses are leveraging social networks for their own purposes. He was particularly interested in how Twitter was used.

To make sure there is no misunderstanding, they aren't a web development company; they aren't planning on building a social network. He just wants to know a bit about how they are used, in businesses themselves and as a tool to advance the business.

I was thinking about the Dell example (how they advertise sales on Twitter), and about how the "fun factor" of social networks can be engineered into traditionally stodgy applications to produce better results (I planned on showing him the beta of Thymer as an example of a twitter-like interface used in project management).

I admit, however, that my expertise is limited, especially compared to the gurus here. HN, please help me end my brush with unemployment! (If this leads to anything, you're all welcome to spend a night or two at my place if you're in Tokyo :) )