People locking themselves into one service provider for everything voluntarily, being completely dependent on it, subsequently missing out on better alternatives outside that walled garden until it blows up.
I think our definitions of "service provider" and "walled gardens" are different. There's nothing about Google that prevents me from using any service that I want and even thought they are integrating many things in more tightly, I still have an incredible range of motion for things outside G+, as well as integrated with it.
I know this is a religious argument - I've tangled with it 9,341,759 times over the years. No one ever wins it - time is the grand determinant.