> It's hard for them to touch: the existing currency laws certainly don't apply. The more-likely scenario of them becoming stores of value and/or securities (legally speaking) gives them little room for enforcement as there is no central issuing party to go after.

The lack of a central issuing party isn't a problem - they can go after any point that converts them to get "real money" or provides goods subject to control.

Physical goods are a subset of the latter.

If you can't buy food or pay rent with Bitcoin, how much can it catch on?