I always figured that

• Agents would act as competitive peers in a market.
• User software would communicate with multiple agents, and replicate accordingly.

Of course it need not be this way.

RE chains:  A chain produces a time-ordered sequence of events.  That's not storage and typically you don't need to store actual data in a chain, even if you do need time ordering.  You just store a hash, then the data may be stored and proven as needed in any fashion.  One might imagine software and agents competing to determine the best replication methods at the lowest cost.