2-of-3 or 2-of-2 for escrow?

[Andrew Vorobyov]

Taken from https://github.com/gavinandresen/bitcoin-git/wiki/BIP-M-of-N-Standard-Transactions (After my edition)

Three-party escrow (buyer, seller and trusted dispute agent). 2-of-3 signatures required transactions will be used. The buyer and seller and agent will each provide a public key, and the buyer will then send coins into a 2-of-3 CHECKMULTISIG transaction and send the seller and the agent the transaction id. The seller will fulfill their obligation and then ask the buyer to co-sign a transaction ( already signed by seller ) that sends the tied-up coins to him (seller).

If the buyer and seller cannot agree, then the agent can, with the cooperation of either buyer or seller, decide what happens to the tied-up coins. Details of how buyer, seller, and agent communicate to gather signatures or public keys are outside the scope of this BIP.

No doubt this scheme will be find its usage among people but how about old one where buyer and seller lock their equal amount of funds until mutually agree to close escrow, I mean no third party involved.

How can we implement that escrow will be locked after both participants funded it and not sooner then it so in event escrow creation fail party can take it's money back

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[etotheipi]

2-of-2 escrow works in 99% of cases, except for when one of the parties "disappears."  What if one party dies?  Goes out of business?  Loses their wallet?  Then that money is locked forever.  If you have a third party, they can assist when this happen.   It can kind of act like insurance, too.  

For small amounts of money, I think the 2-of-2 escrow is fine... but you really need a third key in the mix to make sure nothing goes wrong.