As many have said already G+ did the job on its own. But what's also important was the crucial time at launch. These were the days when the people coming to Fa

As many have said already G+ did the job on its own. But what's also important was the crucial time at launch. These were the days when the people coming to Facebook in 2008, 2009 were a bit fed up by it and wanted to try something else with hosting pictures, events etc. So they actually were the most interested in trying in out, hey it was a Google product and everyone loved Gmail. But Google screwed up and placed an invite system. I don't know if they weren't prepared for the scale or wanted to copy Gmail (it worked once, amirite!) or the Facebook being exclusive at their beginning. The times were different though and if you slam the door before someone eager to try out your stuff, guess what, he won't come back. So after couple months when the invites were a bit more reachable, the initial interest was wasted and left an aftertaste in people. And you don't want that.