The chap in question is Feross Aboukhadijeh from Standford University--a computer science student with a swift coding skills and some spot-on imagination, it seems. The idea is essentially the same as Google Instant: As you type into the custom search query box on Feross' website, the code tries to swiftly match your incomplete sentences to YouTube's archive, and then the lone YouTube window embedded right below updates with the video that matches the phrase most closely.
Try it out. Typing "Fast Company" takes you through a clip from "Fast and Furious 4," through a "fast car," a "fast computer" before ending on Quadrant Films' 1978 classic "Fast Company" racing flick. My name evolves along a journey through a video of Katy Perry,