Read this comment on Supercoin by fluffypony, one of the Monero devs, who explains why n-of-m multisig is not safe:
"The "guarantor" is being trusted to do arbitration between the sender and the mixer. Therefore, given the nature of 2-of-3 multisig transactions, the guarantor and the mixer can sign the transaction, and then refuse to sign the cancellation transaction, leaving the sender out of luck and out of funds."
Also, read this, why using the txid to mixing is not safe:
"Even worse - the workflow is based on the txid and verifying the txid. Have we not learnt by now that the txid can change? How do you people not understand that this was the very thing that mtgox blamed for their destruction?
The issue here is relying on the txid, when malleability has shown that the txid can change. This so-called "trustless system" relies on txid's to confirm transactions in an automated fashion. That is bad, stupid, and fundamentally broken."
Be careful not to fall for new shady coins promising the earth and screaming FUD at more established coins.
It certainly beats me how trusted third parties - "escrow" services, a very pre-Bitcoin thing - are presented as either trustless or anonymous.
m-of-n multisig was not designed for trustless anonymous payments.