Like you, I would also rather that website owners had real incentives to please their users. I disagree on the solution: data lock-in _removes_ the website owner's incentive, instead they can just rely on the fact that you are stuck with them, rather than pleased with them.
We all have to make money somehow. I'd rather website owners had real incentive to please their users, and being able to make money is a good incentive.
I don't see how free data can really be relevant on the web. If facebook want to do something to drive users away, or ristrict users freedom, that's up to them. If they do it enough, someone else will setup a rival website that pleases users better. How does free data fit into this? I don't think it does. Most website is simple enough that you don't need free data. Any one of us could clone facebook's massive social network if we had enough time and determination. Letting users own their data is certainly a nice thing to do, and I'm sure we'd be lost without our own data, but I think it makes less sense on the web.
As I've said before, I don't use X because its data is free, I use it because it's free, and there are people behind it who care.
I think that's all that matters really.