The great thing about Google+ is that you don't need your friends to move there to derive value from it. Rather, it seems to be designed to follow a three-phase

The great thing about Google+ is that you don't need your friends to move there to derive value from it. Rather, it seems to be designed to follow a three-phase growth process, first supplanting Twitter, and then Facebook and Foursquare. The asymmetric connection model makes it easy to fill your stream with enough signal to be useful, much like Twitter. This allows individuals to discover and begin using the service independent of their broader social network. Which is where circles and check-ins come in: If you and enough your friends are already visiting Google+ of your own volition, why go elsewhere to share something with them? If enough folks in the area are already paying attention to Google+, why not check in there instead of on Foursquare? It strikes me as less of a Facebook killer than Buzz 2.0, but with vastly broader institutional support and the tools to scale from that into a Facebook replacement, once your own social graph is sufficiently on board. All it takes is time. Edit: Oh, and sparks! Sparks are great if you want to use Google+ but can't find enough users to fill your stream, yet. It's like googlebot-curated RSS. Again, it gives users a reason to come to Google+, even if their friends haven't.