This is the first time I have joined a professional social network. My previous experience is limited to Facebook, and I use it mostly to keep track of family and friends: being far away from home pushes me to use it more frequently. Some of my fellow teachers use Linkedin, but I have never tried it.
My personal impression is that educational tools, apps and sites are evolving really fast. New ones or improvements to those that are successful, appear each week with the intention to make our jobs easier.
As educators, we need to invest time to learn about them and here is where social networking can play an important role. What better tester than other teacher to comment you about a new site, video, app, conference, research, etc.?
There are multiple ways to engage in social network. Knowing what tools work best is up to each person. But it is comforting to know that, besides our co-workers in our school or job place, there are also more people 'out there' with similar interest that can make part of our professional development much easier.