I remember when we as young (lower 20s) Air Force people would go to similar presentations using a steak dinner as the bait. We got lots of good meals before we started running out of new presenters. I think they started checking to see if we were part of the "free dinner" guys. lol Not sure that was legal for them to do but back in the early 1970s, maybe the rules were different. . . or just ignored.
Learned how to look very interested throughout the presentation and then how to calmly walk out at the break. Great fun for a pretty good meal.