Industries where companies sell directly to the customer, like retail or food. Whole Foods, for instance, has a very active presence in online social media. That doesn't mean they necessarily use social CRM, but they would be a good fit.
Siva - I would say social CRM is industry agnostic. One of the big value props of social CRM is that people across all industries are represented on diverse social networks like LinkedIn, Facebook, and Twitter. Social CRM offers users the ability to cull all that data to create comprehensive social profiles of all their contacts, in an automated fashion. Check out a demo of Nimble CRM to get an idea of what this looks like in practice.
Any industry where customer feedback, or communication with a customer base is important, would probably benefit the most from social CRM, as well.