You think this hasn't been suggested before?
https://bitcointalk.org/index.php?topic=133931.0 This has been told and repeated several times but very people pay attention, it is also vital to add to this that if the amount of trade is big then hire more than one for a multisig address escrow, which adds more security, since there has been instances where escrows itself ran with user's funds, master-p for example.