If you recognize that a hash is equivalent to the content, you realize you have to wrap DRM around the hash lists, just as you would the original content.

Perhaps limiting the cache lifetimes would give some legal protection to network operators. Nobody is sending take-down notices for network caches today, are they? I would love to see this protocol have some legal safe harbor - perhaps based on a limited (24 hour) TTL before requiring refreshing the cache from source (which could just be a "ping" w/o retransmitting the whole chunk).