This is a standard question I get every time I talk about Social Media Marketing to audiences including people from the B2B domain. For many social media is strongly associated with B2C marketing while industrial marketers seem to be quite enthusiastic about it. A recent post in BtoB Magazine gives some nice examples of B2B applications of Social Media; for those interested in some stats I suggest to look to the E-Marketer and this post of Brian Solis. An older report of Marketing Sherpa also indicates that B2B marketers are enthousiastic about social media as part of their marketing strategy. (see table below)
Conclusion is that there is enough talk and evidence about B2B and social media marketing and it seems that industrial marketers are equally (if not more) excited about it than their B2C counterparts. Let's wait for the first scientific evidence on this, I will keep you up-to-date here.