Everything must be "above the fold"
Ever since the birth of the internet, experts have always said that all content and main calls to action should sit above the fold (the area that the user can see on their screen without having to scroll) and that a user shouldn't have to scroll because if there is too much content further down the page it will be missed .
I believe that with the introduction of HTML5 and websites like these:
Scrolling becomes part of the experience, users will want to scroll in order to discover more and see how the content comes to life. Users are suddenly getting a Rich Flash Media experience without waiting for long load times, iPad and iPhone users can finally have an amazing Flash content experience. I believe that this is a complete game changer.
It will also be interesting to see how this effects Information Architecture, User Experience and User Interface principles, it's a completely new way of designing for the web.
It doesn't even feel as if you are scrolling and it gives a website a more tactile / magazine feel, the web suddenly comes to life and the creative opportunities are endless. I also love the way it optimises for mobile without limiting or changing the user experience.