For additional confidence escrows should limit themselves on the amount they hold. They should have a clear public list of the amounts they hold and recommend other escrows when they reach some threshold.
All you need to be sure that the funds in escrow are safe is to ask the escrow provider to combine his key with keys of involved in deal parties (buyer and seller).
how would that work if escrow colludes with one of the parties?
which is what appears to have happened with Master-P and a few recent transactions