High frequencies take more "bandwidth" (not really the appropriate
term
perhaps) to encode than lower frequencies.

Which I guess explains why the most noticable SQ problem in mp3's
recorded at lower bitrates is the swishy highs. Go with 192kbps+ and
mp3's are decent.. 128, meh..

In fact, some folks are simply transferring their entire collection to
wav
thereby leaving it completely uncompressed - screw mp3! Mp3 was
useful when
hard drive space was at a premium.

I havent ever heard of anyone doing that.. I'm sure some do, but at
~50Mb/song, thats only 20 songs per gig of hd space, 200g drive only
holds 4000 songs.. As opposed to 40k in 192kbps mp3.. I dont think
..wav's sound 10x as good as mp3s, so I'll just stick with those..