Well crap, he beat me to the punch. I was going to write an article on data ownership and how we should be able to maintain our own data and only let networks curate and syndicate.
Lol.
Bigger and more influential apps will always roll you into their corner. It's what every single vendor would do. It's what you would do.
Plus, as a user, I don't like analytic data being collected. As a software provider, analytics drive nearly every decision.
I like the spirit of what Solid is trying to do, but as long as targeted advertising works better than randomizing every ad you see (it always will), there's zero reason for any profit-seeking entity to choose it.
The gist of it would be:
If I write something as a tweet, wordpress would be the first to pick it up and possibly manage it. WP would be more of a CMS for your data. Write a tweet, it can be shown on your blog, and possibly to twitter and/or facebook. This would work for other content types. The value of twitter and fb is the network affect and curration.
A simple example is that I would want any food delivery app, or web-connected restaurant to know my dietary data instantly, but not really much else. Any new-media site I connect to I want to instantly know what kind of content I find boring or distracting, but not really anything else.