nostr has yet to solve one its spam problem. and thats where the catch is.
nostr's success relies on its censorship resistance, which in turn relies its tolerance of spam. this means every note is allowed regardless of its contents.
nostr has not yet seen any real spam. in fact almost 50 % of notes are still written by humans. however current protocol implementation does not have any real spam protection systems. this means in future at least 99,9 % of notes will be spam if no new methods for spam prevention are implemented.
however, as said before, nostr's success relies on its spam tolerance. what makes mastodon different is that their spam handling is based on account deletion practice. nostr cannot ban accounts, and nostr cannot limit number of new accounts.
so does a solution exist?
yes and no.
whether nostr wants to solely focus on social media features, there may be a solution. the solution is to limit creation of new npubs. this can be done by two different methods:
1) require pow for each npub
this method will be gamed. this results to asic miners which in fact makes npubs to require a payment in future, because no-one will be able to mine this pow without specific hardware.
2) implement block chain or dag for npub registration = npub registry
also this will require payment for making a transaction in the chain.
so each method relies on payment, which you may think is small thing, but in fact its not. bittorrent doesnt use payments, and that is the basis of open protocols. when you implement payments you tie ecosystem into specific monetary solution, and whatever you think is the best monetary solution, its not. there is no one world currency and there will never be one. monetary ties always require multiple steps, for example: acquire some currency, acquire some wallet etc. at this point free and open protocols without monetary ties go further: for example mastodon, whatever its disbenefits on other areas may be.
now in addition to monetary ties with limiting npub creation it also adds another hindrance, which is lack of anonymity. this property comes from one or two sources:
1) monetary system used may leak data
2) limiting new npub creation does not allow true anonymity, but rather relies on pseudonymity
freedom to create npubs is what makes difference in nostr, yet its the same thing that makes nostr very difficult to scale. massive, professional level, high throughput spam bots will populate nostr event space with their pseudo language bots that create notes faster than you can type a single letter. they create notes that have no inherent meaning, yet they can hide this randomness within bounds of human language, making it costly to differentiate between real and non real notes.
finally, nostr success is not really based on any great invention. its based on two primary inventions which are:
1) local management of keys makes impossible to ban user accounts
2) tolerance of spam on relays
mostly nostr is even possible only because events have limited size and ips are throttled. neither stays really true if vpns are allowed. therefore vpns will not be allowed after a spam bot starts to consume vpn's public ip space.
nostr is great, but i dont think it will work out in its current form, and it will not work with adapted form either, because it will not gain any popularity after npub creation will require a monetary transaction.