FWIW, they did pose a competitive threat to Facebook, forcing FB to add features like choosing which groups of "friends" to show a particular post and letting p

FWIW, they did pose a competitive threat to Facebook, forcing FB to add features like choosing which groups of "friends" to show a particular post and letting people see public posts of people who aren't bidirectionally connected. If Facebook had refused to adapt at all, G+ might have grown more significant.