Recently the comments I used to add for people who followed me on Reader appear on Google+. This makes both Reader and Google+ more effective for me. People can share my comments and this has resulted in more people following me.
As it is easy and obvious to group people in one or more circles, I can target what to share with whom. It is not that I would not be happy to share this on Facebook, it is just that I do not care for Facebook that much. Personally I feel the same way about it my mother does about e-mail; I have better things to do.