I was pleasantly surprised to find a good
article in Rolling Stone about how the sound quality of recent album releases. In short, the dynamics (loud sounds vs quiet sounds) are compressed so that everything sounds loud. This is done so that the music stands out even when listening on the crappiest of laptop speakers. The problem is, even on modest MP3 player headphones, this sucks the life out of the music, gives you a headache, and leads to the downfall of civilization. (... but I'm not bitter.)
For the short story, check out this very well done
YouTube clip.