I think it's all been said already... but the thing is, when I put those sorts of things in my ears, it makes a sort of unpleasant tingling in the middle of my neck (or somewhere, it's difficult to tell) and I just can't bear the ticklishness of it.
Also, I'm lucky enough to run along fairly deserted country roads and I don't think I'd be here to tell the tale if I couldn't hear traffic. A shame too not to listen to my inner self, my breathing, my swearing/encouraging/just alking to myself out loud.
I took up running as my way to honour the memory of my recently-deceased father. I 'took him with me' and he 'talked' me through those first runs/months. Would this kind of 'communion' have been possible with an ipod or other such gadget in my ears? I think not. However, 'each to their own' seems like a good adage and I don't think anyone will really change their habits as a result of this debate/challenge. Interesting though, as always, to read other people's opinions.