Maurizio has a great post about the dismal quality of mp3/ACC audio, and the parallels in crappy video. Actually the problem – for audio at least – is far worse than just the final format:
Dynamic range, warmth and depth have all but disappeared it seems in today’s music recordings. Music is compressed in recording, in mastering, in broadcast; often at all three stages. The loudness effect is ubiquitous. Broadcast audio is so pumped that it never seems to vary more than a few db. What results is music that is shallow, cold, harsh and without any kind of imaging or space.