I was extremely surprised that Google+ didn't catch on. The week before Google+ launched, me and all my friends agreed that Facebook is toast, Google will do the same thing but better, and everyone has a Gmail account so there will be basically zero barrier to entry. Obviously, we were wrong; Google+ managed to snatch defeat out of the jaws of victory, Google+ never got significant traction, and Facebook managed to keep growing and now they're yet another Big Evil Tech Corporation.

Honestly, I still don't really know how Google managed to mess that up.

I got early access to Google+ because of where I worked at the time. The invite-only thing had worked great for GMail but unfortunately a social network is useless if no-one else is on it. Then the real names thing and the resulting drumbeat of horror stories like "Google doxxed me to my violent ex-husband" killed what little momentum they had stone dead. I still don't know why they went so hard on that, honestly.