It’s inevitable that someone will build an unstoppable marketplace. It’ll be something that cannot be taken down using technological controls because even the creators don’t control the evolution of it. The code will be open source – anyone can copy and launch their own version.
It’ll be peer to peer to prevent central points of failure. To incentivize all involved parties the value transfer will happen on open censorship-resistant distributed ledgers.
The control of these systems will be political since everyone is responsible for the software they run. It’ll be interesting to see how this will play out.