[brownbat]

I like that rule, but I would extend ever so slightly:

If existing providers are anticompetitive, blockchains allow you to bootstrap an alternative without the same capital requirements you might need to compete with, say, VISA or Wells Fargo.

I'd also note that transacting across borders can easily make legal remedies cost prohibitive, especially for smaller transactions, even if both countries have mature legal systems. So I expect cross border activity to be more typical than the illegality example in the long run. But that fits your conditions as written, so this is just a quibble.