As much as I am excited to see such hacks, a lot of the HTML5 goodness is just reinventing what Macromedia Flash did 5 years ago. The page turn JS, the audio recording JS, webcam js, etc have all been possible before with Flash quite easily in 10 or 15 lines. Not to mention it has been more reliable (no audio sync issues, no video drivers issues, etc) and it works with 99.3% [1] of the browsers in the market instead of just a few.
Proprietary or not but Flash still fills this need better than anything out there and it is sad to see that the so called better alternative is still in such a dismal shape (even in the latest release version of browsers).
I think the point is that the web platform should be able to do all these things natively.
Right now, the implementations aren't perfect - and cross-browser support is definitely lacking. But ultimately, I think it's hard to argue that the end goal of having this stuff baked in to HTML and JS is better than relying on a proprietary 3rd-party plugin.
Proprietary or not but Flash still fills this need better than anything out there and it is sad to see that the so called better alternative is still in such a dismal shape (even in the latest release version of browsers).
[1] http://www.adobe.com/products/player_census/flashplayer/