Well, thank you for all those responses! (Sorry for the delay in getting back. I'd forgotten I posted this question.) I have read every response except those many which were arguing about previous responses. (As a car-free cyclist, I possess no car insurance.) So, in summary, the real purpose for wearing one isn't prevention of close calls, but in for evidence when an accident does occur. Good to know. As for those of you who believe these little box cameras on the helmets are large, eh, no they aren't. Certainly not. I do like the idea of one of the last responses to just make a little box and attach it to the helmet to make the drivers think you have a camera! I may do that.