Before I go off on to much of a rant, I do want to clarify - having the javascript be the content is fine for a special 'once off' page like the one in the grandparent post. In this case its probably replacing a flash animation. Its also fine for applications where you have a tight handle on the people and devices which will use it.
However as a general practice its a bad idea. A few very important cases that this breaks:
* The googlebot and archive.org
* Vision impaired users
* Services such as readability and instapaper
All of these could be better served by having a symantec table of data, which is then then enhanced and presented in a different manner by javascript.