Agreed. Bots are gonna be a huge problem on nostr eventually, because of how free things are. 
Platforms will have to get creative with tools to combat them. I think different content filters or filters that hide accounts that are inactive/suspicious would be neat only if they are completely optional for the users to implement on their own if they choose. 

 i agree i'm sure there will be many interesting solutions. I feel like a small lightning deposit is another potential solution i'm not sure how it would be implemented but adding some sort of real world cost to spinning up a bot could be very effective.