removing the cost for real users to join and contribute to the network is an existential problem farcaster needs to solve

most people don't pay for social media - doesn't matter if it's $1 or $10 - it's not something they're used to

this is also an existential problem for apps building on farcaster

If you remove cost, you have infinite spam.

If you gate sign ups, it's not permissionless.

Warpcast has tried a couple of large, reasonably scaled experiments with free sign ups and the long term retention rate is basically 0.

I've seen many times a lot of spam in cost-only environments too, I mean arguably on Blockchains there is the most amount of spam, we all have hundreds of spam NFTs in the wallet.

Cost can be a barrier to spam when there's no cost-benefit for the spammer, but making a cost that high is a death sentence for any social network. 

No cost seems the best approach to social networks, as many people feel that their participation is enough of a cost. If that participation can have any extractable value it is the job of the social network, not the user.