I think a reputation system is mandatory, but it could just be a low-tech review system. Agoradesk for P2P crypto transactions was successful with large amounts of money (trust) because traders accumulated large numbers of positive reviews. So the proof of principle exists. I don't think agoradesk could have been successful without the review system.

yep, clients could easily implement basic auditing thanks to nostr's event history. basically zero code. you don't even necessarily need manual, prose reviews - a positive paper trail of pro-social behavior goes pretty far. (of course, implementations could add reviews trivially as well with existing Kinds. this could be a distinguising feature that might attract users to your client) GrapeRank is the ultimate end goal. but we can get really far with just basic nostr events for a while.

Building the agora for labor for pseudonymous contract work:

I wonder how an insurance agency could possibly be instantiated on such a platform, or if that is something better left to other realms. It looks like arbiters are serving a very direct escrow and insurance role in this scheme, but I think another good input to this might be a betting market wherein the future reputation, price, or profitability of the arbiter himself relative to others may be a subject of speculation and bets may be made on this account. This way you may hedge your bet on an unproven arbiter by placing a small bet against your own judgement, and you can also use the price of these bets as a more accurate and precise measure of the consensus on reputation.

This would effectively protect you from being screwed too much on a critical job, and it would also, if the betting market is very public, provide an excellent and immediate feedback using all available information on who to "trust" and how much to trust them.

that's super interesting! I have a little bit about insurance on the Use Cases page, but it was a quick brainstorm. I invite you to write stuff up like this and I'll post it on the site somewhere!