Oh cool, it can be very useful for pages like Javadoc, even if you are in the middle of the page you have always access to this Table Of Content so you can navigate rapidly, I think a greasmonkey script could be useful to run the bookmark automatically.
I like the styles too.
I think that's a great idea. Particularly useful for Wikis and the like.
This is based on what MSNBC.com does in their news articles. It's really quite brilliant.