A recent contribution by Russ Nelson of Conifer Research is worth reproducing here:
Enough adults now have profiles on social networking sites–about 35%–that the fear or ick factor is going away.
As a result, social media/web 2.0 technologies are slowly being legitimized as business tools to improve communication, collaboration, and productivity (in part by reducing the amount of email). In my mind, it’s really interesting how technology is now being developed by and for consumers and then trickles into the business world. For so many years, it was the other way around (email, computers, cell phones, etc. all began as business technologies).
HP Labs is one of the many institutions that is studying the effect of these tools. I am sure that others on this list know of countless other sources for research in this area.