Whippets kill. (Mostly by making you fall off the chair onto the hard tile kitchen floor. But... holy shit... exploding whipped cream dispensers?!?!?)
I've spent twenty minutes trying to figure out how you end up dead from a whipit and it looks like the restraining cuff on a particular brand of French chantilly cream dispenser cracks, thereby not retaining the whipit against the vessel and instead launching it against a very small and unprotected sternum. Gotta love the headlines, though.
My understanding is that the shell of the cracker splits. The pressure wave inside, directed at the sternum, is enough to stop the heart. Maybe if the seam split away from you, you'd just suffer a broken sternum from the impact of the cracker on your chest. I have no idea what the pressure is inside those things, but letting it escape explosively in any direction ain't gonna do nobody no good.