This is actually how some Bitcoin transactions take place, on the white, grey, and black markets. People build a reputation for honesty as an escrow, take a small fee, and facilitate transactions. They arbitrate disputes, and decide who to release the funds back to.
I guess it's more the acceptance that buyer/seller is an adversarial relationship so you need to at least be able to trust the system or framework to be impartial and enforce honesty.
No, escrow is trust-as-a-service. That is, it's a means of removing the need for trust between the transaction principals by hiring a mutually-trusted third party.
