We banned insurance companies from making decisions on genetic information long before any actually tried it. No one had to make a personal nuclear weapon for us to make it illegal. Plenty of examples of how this isn't true in society.

A significant potential and likely harm is enough to consider preemptively regulating.

You're thinking of regulations. In basically every manifestation the primary function of the state is the enforcement of basic property law. If you don't have that you have warlords/oligarchs fighting with each other constantly over who owns what (since they each individually must act as enforcer).

As far as enforcement of property right, the "distributed" model is well understood and typically leads to a much worse situations than the centralized version.

That only works for things that don't depend on a legal framework to be useful.

Some of these blockchain applications are essentially proofs of concept waiting for a legal framework to support them. But until that framework exists, it doesn't make much sense to use the applications for anything that involves real value.