With the new wave of script kiddies using that free market script i got to know about multisig. I can't see how it is any safer.
If market owner is a scammer. Instead of running away with escrow money he just make several fake seller accounts with the best prices, verified status, old fake register date, hundreds of fake positive feedback and always keep their listings on top search results. By doing so he makes thousands of sales in a very short period(maybe all sales of the period) and run away with the money, he is both the seller and the third party who has to agree.
Well, multisig is just a lot more complicated and time consuming and not safer. It is actually a step downward.
The problem is, you have to attract the heard. That is sort of difficult when many find you fishy...