...actually, I would say that people paid for hand wavy nonsense about a general purpose pipe for applications, and instead got a Twitter clone. :P
I love app.net, but I never use it; brass tacks, most people are still on Twitter (which is itself a small player compared to Facebook). I'm rooting for Caldwell and I applaud what he's going for, but it's going to take some very clever disruption and/or pivoting to unentrench or sidestep the social momentum of Facebook and Twitter (even Google with its billions isn't really cracking that nut). Federation would be the best approach; it's just a shame that that the nuances of social networks make it a much tougher problem than with email or the web.
One potential path might be to integrate with hardware and offer some sort of "self-hosted identity as a service", an encryption-heavy digital break-out box that provided web, email, distributed social network, Dropbox-style app integration, etc. The initial buyers would the people nervous about recent spying revelations, but if the UX was compelling enough, it might have enough other consumer benefits to cross over. I can dream, anyway. :)
That appears to measure G+ for the purpose of logging in to third-party sites; and I'd guess that to most users doing so, they think primarily in terms of their Google account, or their Gmail account. I've heard of very little traction with "regular people" for Google+ itself; Facebook still reigns king there.
I have very little idea what service they are actually offering. There's a twitter clone.. but also you pay for some sort of file hosting, and I'm not sure past that.
I believe what they've put up is designed to be bare bones, and my guess is that they're building something much better if they were able to raise millions more.
He's also gone into great detail on his blog about how unsuccessful that has been and if he worked on the port himself (outside company volunteered to work on it) he wouldn't have been able to go fulltime like iOS allowed.
You don't really get a choice about lock in, however you do get to choose if you want your actions, searches, communications and location harvested to build an advertising profile or not.