Is listening to music dangerous while cycling? This wouldn't apply to riding technical trails or anything challenging, but are there any reasons to eschew the tunes while riding?  Noise canceling earbuds would probably be hazardous to myself and others, but provided I can hear what's going on around me, is there any reason not to?

edit - it almost seems wrong to edit and make some of the answers sound off, but FWIW, I was asking in reference to riding places without cars.  Parks and such.
It is worth noting that deaf people cycle perfectly well.

@Joe's excellent comment merit's adding into the answer...
Edit It should also be noted that deaf people are used to being deaf. They never rely on sounds like hearing-abled people do. 

Its OK to listen to music as long as 


a) you are aware that you don't have any audio clues to hazards
b) don't put yourself in a situation where you rely on audio clues
c) you compensate with very alert visual monitoring of your environment.


That said, I don't listen to music while cycling.