It’s an option for anyone to use I guess for every note, or perhaps if relay are rejecting them with PoW minimum. If you’re not a member, it could be an ok way for relays to generate income - or pay costs.
In early testing you need at least 20 PoW to start to combat spam and automated flooding. That’s more than a laptop or mobile can do in a second. So around there may be the starting point.
Plus, if you PoW once, ideally your pubkey event now is accepted by any relay with a minimum PoW that’s same or lower.
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