Google+ had some clever ideas: Circles, Hangouts, integration with Google's ecosystem, etc. But it was designed from a top-down product strategy. Google didn't necessarily make a mistake by trying Google+, but made a mistake by failing to recognize that social graphs are infrastructure; treating social networking as a new product to bolt onto Google, rather than recognizing that Orkut already contained the social graph and behavioral lessons Google needed.

I _really_ liked the "hangout" idea of Google+. Where you could just start a video call and whoever among your friends wanted to join, could, without having to accept or reject an actual invitation to them specifically. I could work on a project out in the garage and people could hop in and make small talk while I was doing stuff. It was great.

It doesn't feel like there is a great modern alternative to this.

Then they finally shut the thing down just in time to make sure that it couldn't attract any kind of exodus of unhappy users from Twitter or Facebook.

I also think it would've been great if Google+ had leveraged Google Reader and its sharing functionality.