Interactivity in website design seems to be growing all the time, but mostly from an animation point of view. We don't see much of raw video itself being manipulated to provide interactivity. I have dabbled in interactive animation myself when I created my portfolio interface in Flash about 4 years ago. There's a certain amount of consideration the designer should bear in mind about usability. It's sometimes rather easy to get carried away with the way you're adding the content; you forget that people are impatient and require easy access to the information for which they are looking.
One example of somebody who went a bit overboard with the interactivity in their website is M. Night Shyamalan. Sure it's creative, it sets the mood well, but there's no alternative navigation to allow the non-gaming community easier access. I could most certainly imagine my mother giving up on figuring out the website within 12 seconds after being given the controls. Maybe after she obtained the information she was looking for in the first place she'd be more inclined to appreciate the websites construction and interactivity.
One fantastic example of animation in web design is Jim Carrey's website. The designer went completely overboard with the crazy interactive madness, but there's still a bar at the bottom for a simpler navigation alternative.
But I digress, all of this is still animation. When I think of an interactive movie on a website, I think of the old movies that would prompt you to make a decision to progress the story, thereby affecting the outcome. Well I just so happened to stumble across exactly that on this website. It's called Survive the Outbreak, and you are prompted throughout the movie to decide which actions to take to survive during a zombie apocalypse.
Still, this interactive video is not being used for the actual website's design. The only example I can think of (that I know of) that uses real video footage in web design no longer exists. Allstategarage.com used to use Flash to combine a number of different videos into one interactive experience, and there would be some guys building a bike in the garage while you navigate. Luckily, after a little digging, I seem to have found some video footage and screenshots on this website that show what the old allstategarage.com used to look like.
I found an interesting example of something I had never thought of before in interactive online video. James Cameron's Avatar Pandorama takes the video footage from your webcam and attempts to key out your background to put you into the world of Pandora. As you move your hand toward the plant life, the plants move as though you're touching them. I've seen this sort of technology with the Xbox Kinect, but I've never seen it online used with a webcam before.
We have definitely made some interesting and revolutionary progress in online interactivity since I first used the internet in the mid 90's.