A number of posters are spieling out the nanny-state line of Ipod listeners being fools, but no-one will accept my challenge to creep up on me on the bike.
As I have stated before you wouldn't be able to, that's because when I ride, I ride aware of my surroundings.
When I am walking, I walk in a straight (predictable) line, and if I go to change direction I look over said shoulder to make sure my actions don't inconvenience others. When I ski I am quite safe, as I look in the direction I am about to turn so I don't come into conflict with others.
The ONLY reason there are crashes where two (or more) parties paths converge is due to one or more involved parties driving/riding/skiing/walking/flying, and changing direction (into the path of another) without looking.
It's a simple thing called foresight and planning of movement.
It is seen that driving should be a 'right'.
Sadly, a vast majority of people who take up this 'right' are not fit to do said activity, and shouldn't be trusted on the streets with a motor vehicle, not to mention a partially-laden shopping trolley in a supermarche.