Earbuds can be hazardous. Not only can they block out noise (well, certainly not the ipod ones but anyways), but the string can get tangled. I know a rider who just puts the volume on full on her phone/ipod/mysterious piece of technology and it gives her about an 8 foot bubble of music, like a quiet portable speaker which she riders with. Some people do ride better with music and I think this is a safer alternative than ear buds. I am personally old fashioned, I only will use a stereo in the arena/barn or no music at all.
"The trouble with the world is that the stupid are certain and the intelligent are full of doubt"