DCG suggestion seems interesting, but I seriously doubt it will help much in larger transactions - say over $1000 USD.
Accepting payment via credit card is asking for trouble whether one does direct through their own merchant account or via PayPal, etc.
Problem with DCG suggestion is that it doesn't take into account the potential "stolen" / "unauthorized" credit card use scenerios; "friendly fruad", as often seen in the adult business, is difficult to protect oneself from unless one has a signature and an imprint of the card (alternatively, a faxed copy of both sides of the card plus govt issued photo ID - offers limited protection in a chargeback situation, but can be sufficient in some instances).
In regards to contracts, etc - they are basically useless unless the other party has funds, property, etc that's relatively easy to go after ... otherwise, all the contracts in the world aren't going to make a difference; law enforcement won't get involved in most civil matters unless the amounts are very large and/or the situation is very unique ... can require much public pressure, persistance, etc ... and even then, even if the fraudster is tried and convicted, they'll likely serve little to no jail time ... and don't count on much, if any, restitution ... can't get blood from a stone ... one could get even with them other ways, but that will result in one likely having to sacrifice some of their life in prison in doing so ... but the point remains, one likely won't get their money back no matter how many contracts they have if they're dealing with a fraudster who has little to no money, etc.
Escrow.com years ago was great - but lately, from what I've read, their system can leave one or more of the parties in a bad spot. Not real keen on Sedo ... Moniker, on the other hand, appears to have a very good reputation in regards to escrows - I'll likely use them for future large transactions, though escrow.com's system is fast and good enough for dealing with known, trusted buyers who already own a fair amount of assets; have something to lose themselves.
In a nutshell, folks who trade in domain names should who know they are dealing with and understand the difference between revocable funds and non-revocable funds ...
Revocable: PayPal, Credit Cards, Debit/ATM, eCheck (ACH), Money Order, Cashier Check, Certified Check (really? yes ... ie. it's later discovered to be stolen/forged)
Non-revocable: Bank Wire (darn near impossible to recover such funds once sent), Western Union / MoneyGram (upon cash being received - such wires may be reversed in some states prior to being "received"), e-gold, cash.
Ultimately it comes down to trust and taking the necessary steps / precautions to ensure a smooth transaction.
Ron