A similar idea was tried, by one of the largest tech companies in the world, pushing it on to their already established user base, and it didn't catch on. Will it fail again? No idea, but it doesn't imply nothing.
G+ actually worked, it just didn't hit as big as Google would have liked. I used it mostly every day for a while and was sad when it disappeared. So I guess you could say it "failed" for one set of criteria, but may not "fail" if the criteria is a little less demanding.