Yes, manufacturers of all sizes can benefit from social networks - actually, call 'em "procial" networks to be more accurate.
These models can have a huge impact on the quality of customer service, marketing and prospecting. Many large manufacturing companies are leveraging communities like Second Life, LinkedIn and MySpace to help build brand, improve products/services and expand their markets. More are developing whole sites dedicated to serving both their external and internal customer bases.
Small and medium sized manufacturers (SMMs) can (and should) take advantage of the former; but the when it comes to the latter, it gets difficult. And expensive.
Enter Ning - a Web site that lets anyone start and manage their own "procial" network. Now. For free.
If you're an SMM, you really ought to look into this as a viable option. For inspiration, enter "manufacturing" in the search box on Ning's home page and check out some of the communities in place now (or just click here).
Ning was founded by Marc Andreessen, the visionary who brought us Netscape. His personal blog is here http://blog.pmarca.com/. I find him to be incredibly insightful, aside from his seething anger against the newspaper industry.
Additionally, here is a phenomenal networking Ning for supply chain management professionals. It was founded by Atlanta's own Chuck Zdrojowy an accomplished supply chain pro and networking guru. http://scmprofessionals.ning.com/
Enjoy!
DL