Under different conditions this would be an easy backdoor for a recruiter to sneak in for free as a candidate to quietly gather resumes at the event. But since

Under different conditions this would be an easy backdoor for a recruiter to sneak in for free as a candidate to quietly gather resumes at the event. But since you only permit 20 candidates and 20 jobs, the event is small enough that you should be able to recognize this if it happenes. Of course, whether you could do much about it is another issue, short of physically ejecting someone from the room.