I gotta disagree with you there, Glenn!
While this certainly isn't an OS X question, it is DEFINITELY not a networking question! This question is about browsers, and browsers are applications, for which we have a dedicated forum.
The problem with Myspace is the crap people put on their pages: Flash-based audio and video clips, Windows Media clips, MPEG and QuickTime, often on the same page (thus forcing the loading of multiple plugins), plus awful, awful cut-and-pasted layouts with horrible CSS and excessive use of transparency (with fixed page backgrounds) that require tremendous CPU time to render.
tooki