Coinjoin does not require you to trust anyone when it comes to the monetary aspect; you are not putting money at risk.
It works like this: one person creates the transaction and then sends it out to everyone else, including you, let's say. Then you look at the transaction and check that it pays you the correct amount. If it doesn't, you don't sign it. There is no possibility of a transaction happening if you didn't agree to it.
Note - this is *not* multisignature, it's intrinsic to any Bitcoin transaction. Every input to a transaction must be signed by the private key corresponding to the public key referred to in that input. In other words, Coinjoin is just how Bitcoin works, it's just that usually we don't pay attention to it because all the inputs are from the same person.
Well, not *literally* - coinjoin has nothing to do with buying products for bitcoin. But as an analogy, yes, you're in a position just like that - you don't have to sign off on a transaction until you know exactly what you'll be getting back.