This is supposed to be an ezine for people that want to get "Great" on the platform. Sometimes that entails a little calculated risk.
If someone comes into the session late I might stop what I was doing and say, "Why were you late?" 98 percent of the time, the person will tease me back, give me a smart alec answer back (not really maliciously), or in some other way go along with the fun. The voice inflection I use obviously says I'm just playing and not trying to embarrass them.
I would say 2 percent might act a little irritated because I pointed out the obvious. I can tell you in several thousand presentations, not once have I received a negative comment or bad evaluation because of saying that line. (That doesn't mean, of course, that someone didn't think poorly of me because of it --they just didn't say anything about it)
When someone gets up to leave the room during his presentation a comic speaking magician I know stops the performance and pulls out a hall pass from his briefcase and runs over to give it to the person. It brings down the house.
Besides their comic effect, these activities of stopping what you are saying have a practical use. Someone arriving late or getting up in the middle of your presentation is very distracting to the audience. If you keep talking over the distraction, the audience won't hear what you're saying anyway. You may as well sneak in some comedy since the audience's mind is elsewhere.
Teasing the 2 percent can be hazardous to your evaluations so be careful and make sure you've established a likable playful demeaner before teasing people without permission.