Google desktop comes with a pop-up notifier for new mail, as does Thunderbird. I assume that other programs do too. These are not like the old-fashioned biff-ish ones, which simply showed you had mail of some sort. They pop up a box with the headline and sender in it, so you can decide what you want to do about it. Herein lies the problem. Quite often the mail that gets through is spam with graphic, even pornographic headlines. So there you are at the lectern, powerpointing away, and a bubble appears on the screen behind you “Excited young ladies are very friendly with men who resemble animals” it says — or something similar.
All of a sudden, your audience is much more interested. When I think of it, something like this must already have happened somewhere. It’s not the sort of thing you would talk about afterwards, unless you were in the audience.