Very good question, I am still thinking through it, but here are some preliminary thoughts.

I think that spam will become a much bigger problem as Nostr grows. Obviously we will need a way to manage that to stay successful. Since Nostr is permissionless, the onus for spam filtering will fall on relays and end users. With the advent of ChatGPT and successors enabling the generation of infinite variations of natural language, that approach seems likely to fail. I therefore consider it likely that Nostr will turn to the concept of value-as-a-filter; only content with a sufficient amount of sats attached to it will reach its intended audience. It is not clear to me if this is very hard to achieve. Maybe there are simple/organic ways in which this can happen (e.g. just by getting "zapped to the top"). But I would consider Nostr a failure if it takes a large degree of luck for an outsider with great content but no sats to grow their reach in an efficient way.