According to an article from InternetNews Dell has generated over $1MM in the last 18 months by posting sales and promotional messages out to their Twitter followers.  The Dell Home Outlet currently has over 3000 followers.  Although $1MM is not a huge amount for Dell the example does show that the Twitter audience is somewhat in the buyer mind set.

This is a pretty standard use of Twitter in these early days of the service.  Companies are creating Twitter accounts to push product information, special offers, or customer service updates.  Once Twitter determines a business model I’m sure there will be additional opportunties for marketers to leverage this micro-blogging technology.