Gigya analysed which networks users log in with when they use social login, across Gigya's client base. The data showed that, while Facebook is still largely the dominant identity provider, Google/Google+ has made consider gains.
You can see how this differs between sectors. With ecommerce sites much more likely to use Facebook graph than any other log in.
Sharing data reveals that Facebook again is the largest force but Twitter and Pinterest have become quite prevalent sharing destinations as well. In fact, in ecommerce, Pinterest actually receives more shares than Facebook.
It could be argued that a Facebook share is worth more than a pin, but obviously a lot of the value of a share depends on influence of the user.