If user adoption of G+ follows what I remember from MySpace and Twitter, it may play out something like this.
In the beginning, you connect with your “real” friends. Then, friends of friends begin adding you. Then, serial social adders – you know, the ones looking to game social proof – begin showing up in your notifications.
Some early adopter, forward leaning brands join in, but most are waiting for scale in the hundreds of millions and a way to easily place advertising dollars. Then the spam accounts start flooding in: multi-level marketers, fake profiles with racy avatars, bots.
At that point, users start talking about how the early days were better, when you could have a “real conversation.”