The single most important fact that web site owners forget is that the web belongs to the viewer. It doesn’t belong to the web site owner; they don’t control how the viewer will use the site.
This video is a perfect example of this (3 minutes, 30 seconds):
The viewer has tools like user css, greasemonkey, stylish, No Script, and AdBlock Plus. These tools block, alter, enhance, or add to the web as the viewer visits sites. What the viewer sees may be completely different from what the creator intended.
While the actual technique is interesting, it is even more interesting to see the audience’s reactions to the removal of the MySpace cruft.