Would you be surprised if news broke that Facebook has been selling your private messages to third parties? Not really. What if Google did that? That would cause uproar, so G+ is competitive in terms of user control.
Is there a tradeoff between user control and social connections that users face when using Facebook? Were this the case, G+ would have much higher market share and users would have already started flooding away, with the network effect in play.
But that's not the case. Control is relatively negligible to the majority of Facebook users. Competitors won't succeed until values change.
Personally, I value control. I'd be done with Facebook were it not for its White Pages functionality - with a name, you can find someone and contact them. That's not the case for the majority though, so having other competitive systems won't do much good.
People keep talking like some magical Facebook competitor is just around the corner, ready to take on 400+ million fleeing users and assume its position at the top.
It simply isn't going to happen. The ghost town that is Google Plus is showing exactly what most competitors end up looking like.
The groups of people you communicate with are different. Just like during the 90s, some groups used AIM, some MSN, some ICQ...