I've found generally I can operate with almost complete trust, but there are always some bad actors AND people fuck up. Of the latter: programmer contacts me about a job I'm advertising. I tell them about the role. They want me to represent them but decide the best course of action is to apply directly to the client on their website (?!). When I find out, I contact the client and try and explain the situation.
First time I've worked with the client, and after some emails, they grudgingly accept that I have the emails to prove the situation, but the candidate fucked it all up ... however, this has engendered enough shitty feeling that they decide they don't want to continue working together.
I don't get paid for most of the candidates I put forward for roles (employers want 4-5 applicants per person they hire, at least), as they don't get the roles, and can't afford to just forgive a $20,000 commission because the candidate managed to gum up the workings.