At least this thread isn't boring!
For a group that tends to be techno, citing one example to support a point isn't terribly scientific. Jon Allen's article was pretty credible. Life entails risk. I've seen no solid studies that show cyclists wearing headphones get into more accidents. Perhaps the study hasn't been done. However:
Cell phone users have accident rates equal to those with blood alcahol levels of 0.08, a DUI in most states. Still talking on your cell while driving?
Coffee drinkers double their accident risk. Apparently, when the hot coffee spills . . . perhaps they could offset their loss by suing Mac Donalds. Still drinkng coffee while driving?
Most accidents occur within a few miles of home, so perhaps we should only take longer trips? (Clever spin to that statistic, isn't it?)
I guess we shouldn't get into all of the other activities that distract drivers.
Anyone ever trip over something while wearing their headphones? Were you distracted? Perhaps you would be safer if you could have heard a voiced warning. Perhaps you tripped over the chord. If you are reading this, you probably accept the risk.
About all you can do when riding a bike in traffic is to dress in bright, geeky lycra and wear a helmit so drivers recognize you as serious; hold a stead, predictable line; use your eyes and don't trust your ears without looking; try to make direct eye contact with drivers; clearly, emphatically signal your intentions; and try to pick safer routes.
I ride more frequently without than with headphones. When I do ride with phones, I accept what I believe to be a minimally increased risk. Impaired drivers, careless drivers, road hazzards, insects, and sunlight probably offer greater risk.
If you know that riding and wearing headphones that permit you to hear outside sounds is dangerous, that's a faith-based opinion rather than a fact supported by science. If so, then you know that I'm an idiot, completely wrong, and the average IQ of the bike-riding public will increase after I'm killed by a coffee-drinking, DUI, SUV driver that's talking on a cell phone.