As the web currently stands, if you put something on it you have already lost control, so framing the question as one of "owning your own data" is misleading.
I've up-voted the question because I believe it's important and should see a discussion of how future systems might be able to handle this, not because I agree with the implicit sentiment. Personally it would be fascinating to see a real world implementation of the "Oubliette" as given in Hannu Rajaniemi's novel "The Quantum Thief."