Or use an escrow service / middleman that people trust.

Bitcoin transfers aren't the problem here. Its transferring money to a trusted 3rd party, and then that 3rd party transferring the money forward (or back) once the items are confirmed to be transferred.

The problem then becomes dispute resolution. Even priority mail can be faked. Close the envelope with fake cards or whatever... so no matter what, dispute resolution becomes the limiting factor.

But a trusted middleman using a protocol that is hard to fake with harsh penalties on the scammers that do break the protocol is the answer.

Too bad escrow service in eBay means pretty much "you're getting scammed"

By 'these sorts of trades' I meant 'trades with strangers without a trusted third party'.

Of course a trusted third party obviates the need for complicated schemes.

Which are the best ones?

This one looks totally legit: http://cardingmafia.ws/f60/

"Forum: Carding Mafia Escrow Service: Do you need to buy in safe way And Not To Get Ripped From some kid ? Come here and use CM Escrow Service Its Free.. Warning Not allowed To reply in threads .. who allowed to reply in thread just seller and buyer and escrow man anyone else will got banned for 7 days"

Pulsating banner ads: $0.00

PHPNuke discussion board: $0.00

Blinking animated emoticons: $0.00

Mafia run escrow service: $0.00

Knowing the little bastard will end up with a decapitated horse head in his bed if he doesn't pay up: priceless.

Noterized letter of intent works too for domestic sales. Not anonymous but keeps people honest, and gives you option of small claims court.

I think that even an honest unemployed 22-year-old would not be willing and able to find a notary as part of the deal.

When I was 18 and needed to get a letter notarized, it cost me $35.

You (or, at 18, your parents) probably have one or two friends who are notaries. Most banks have some on staff and they're usually willing to notarize other, non-bank-related stuff for account-holders too.

Not everyone is solid/upper middle class...

I meant those as helpful suggestions but...ummm...thanks for the reminder. Also, you'd be surprised who is a notary. It's not all high-end finance people. I know one who works as a receptionist at a car dealership.

Earlier this year I needed to get something notarized. Went to the UPS store 3 blocks from my work, paid $5 per signature (=$10), walked out 5 minutes later. It's a hassle, but for a $500 transaction it really isn't such a big deal.

You can just search for them on Yelp.