How does this prevent developers from still copying your data and storing a copy on their own servers for faster access?
By what I understand you could choose to host your media on one server in a standardized way and share them via as many other services that you want.
For instance imagine Facebook, Twitter and Dropbox comply to this standards. You put your content on your Dropbox and share it on FB and Twitter. Now with solid if you erase your data on Dropbox its erased on FB and Tweeter too. If you delete your Facebook post, the tweet don't have to be erased as well. And should you want to leave Dropbox for whatever reason you can download standardized data and upload it to a new solid compliant server of your choice and keep link working by simply updating url to your new server. I haven't read the git now but this is how I picture such a stack. And this is definitely the missing link of today social networks in my opinion.
So basically it's about not being kept captive because of the contents you've put in today's social media.
But I don't see why solid would be worst than today. You will still have to trust the different a services you link to your data. But unlike today if one service mess-up badly you will be able to switch to some other service.
Should we learn tomorrow that Facebook is evil, currently most of the users would rather keep going rather than delete their account and loose everything.
(Full disclosure I left Facebook one year ago)
Right now, just having user is data is only 'OK'; up-to-date user data is the real goal. People, particularly every marketer's favorite demographic, teenagers, change their tastes and interests drastically and frequently. Just knowing Jenny liked Justin Bieber when she was 12 is almost useless when trying to market to Jenny at age 15.
Into the future 'old' data will further reduce in value as app developers make up-to-date and other hyper-targeted data more available.
If you don't want it copied all over the world and archived forever, don't put it online.
The point is that you decide where your data sits and who has access to it, not that it's free-for-all.
Unless I misunderstood your point completely...
Personally, i take "data ownership" as a hosting issue. Where it originates from, where it lives. Not specifically protecting anyone from copying it. Eg, Facebook is a sort of vendor lock-in. You end up entrenched in their platform, because your content cannot be swapped to, so, Google+ with ease. If you had true ownership of the data, you could theoretically swap as your desires dictate.
If your idea of ownership was true (assuming i'm understanding you correctly!), then that would mean Twitter, Facebook, etc don't actually own your data either. Because you can copy your Facebook data. There is no lockin with Facebook, and our problem with ownership is that someone else in your friends-list can copy/steal your data?