I see that spam filtering is being handled, but simply blocking known spammers every time isn't a real solution. Eventually, is WOT (Web of Trust) the only answer? Or perhaps a PageRank-like scoring system based on extensive collection of kind 3 events? I'm also curious how your relay operates. I've considered attaching tiny amounts of e-cash as economic incentive for relay operators, which could contribute to a healthier ecosystem. But since events are commonly pooled and broadcast simultaneously to multiple relays (especially since there are usually several tagged recipients in a p-tag, and each user likely has at least two or three inbox relays), I'm not sure users would accept the added complexity. Plus, managing different policies(price) across relays would make implementation quite cumbersome.