More broadly, "The US legal system is not prepared to deal with bitcoin" is not the source of systemic risk that you should be terrified of.
I see what you're saying, but how can you prove ownership of bitcoin? Is is just having the private key? Someone hacking your system can get that. Online wallet services have that. Does it mean being the first one to generate the wallet? And even if you have some way of proving ownership of the wallet, how do you prove ownership of the bitcoin? The ownership of property in the US is backed by the US government, and the US government backs property transfer. You can't just take stuff by getting 51% of the population of the US to agree that the stuff is yours.
EDIT:
Another point: I get your private key and send all your bitcoins to some other wallet. How do you prove that I was the one that did it, and that you did not agree to it?
If you want to see what might have happened when digital object is truly stolen, try looking up what happened in this vague case.