I remember and old Creem magazine I had in high school, where someone said "No one who truly loves rock and roll uses headphones." ...and it was true! Everything was about big speakers, and quasi-high end stereo systems. I remember a guy who had giant home stereo speakers in the back of his Mustang...haha. People didnt want to play an album over again because it was supposed to degrade the sound quality.
There was a lot of hype attached to all that, of course...but nowadays the whole concept of "sound quality" has completely gone out the window with MP3s. And what about older recordings with lots of stereo seperation? Just because an instrument is only coming out of one speaker doesnt mean you're supposed to hear it with only ONE EAR.
But yeah, Im mostly in front of the computer with a pair of cheap sony headphones on.
Check out David Lynch's "commercial" for the iphone: