Is There Any Benefit to Professional Social Media Networking?

I was automatically enrolled in the network LinkedIn through my professional affiliation with the Appraisers Association of America. I invested some time in building my profile including recommendations by colleagues and joining Groups.

My question is what is the benefit of professional social media networking if it doesn't create business revenue or find jobs? Or does it? Is Facebook more effective than LinkedIn?

Any comments, suggestions or words of advice can be sent to me directly at afp@nyc.rr.com

Thanks
Anita