I agree that there are a lot of cases where social media is used as the mechanism for narcissism. However, there really are benefits as well. Definitely not as many benefits or as much ROI (with time spent) than the industry expertise profiting from the craze will tell you. It also completely depends on the industry that one is in. The aspects of social media I find somewhat useful are some Facebook groups (mostly photography groups local to my area) as there are some good conversations and community supporting each other which is nice to see, Tumblr for sometimes getting a sense which of my art is more marketable (for what it's worth), and LinkedIn for various groups and potential business contacts. Twitter I don't use and don't think benefits me in anyway. I don't really have time to use social media heavily (nor do I think if I had extra time it would be spent wisely on social media) but I do think it has it's place if used wisely. I never really browse Pinterest but do know that there is some very clever and creative ideas there.
Cheers,
Jay