I'm not sure if this can really help users protect their data. Tons of personal data is already out there, and companies that want it can buy it fairly readily and cheaply. Users have shown a willingness to exchange personal data for useful applications. Tons of data isn't even individual; who owns your personal social graph?
PII is the most circulated currency on the internet and anything that stands between companies and their cashflow (privacy/data ownership projects like this) seems like it would be a nonstarter.
I don't think those are invalid points, but one consideration is that if a standardized format for encapsulating and controlling PII did emerge and was adopted, the value of the previously-released personal data would decay over time.
That is, if your current PII suggests that you are a fan of (Brand X) right now, it is more valuable than if it shows you were a fan of (Brand X) 5, 10, 20 years ago. There will still be correlations that can be drawn from historical data, and some data's value doesn't decay as a function of time (DOB, for example), but it would still be an incremental improvement over the current system.
As technologists, I don't think throwing up our hands and saying "It's too [late|difficult|expensive] to solve this problem!" is the right solution in most cases.
Not immediately, as others have pointed out, but those who develop products that incorporate this approach, and those who embrace it swiftly, will provide us choices.
For example, if "MeWe" were to incorporate this I think they would grow faster and at some point put enough pressure on Facebook to do the same.
PII is the most circulated currency on the internet and anything that stands between companies and their cashflow (privacy/data ownership projects like this) seems like it would be a nonstarter.