The first public demo of a Web Forms 2.0 page was actually a very high profile demo, though I highly doubt that anyone present actually realised they were looking at it. It was during Steve Jobs’ keynote speech at Apple’s Worldwide Developers Conference, during the Safari RSS spot. If you look at the top right of the screenshots of Safari showing an RSS feed, you’ll see a little slider control. That, my friends, is a Web Forms 2.0
<input type="range"> control.