Yeah, but stage6 will be closed tomorrow, so we have a choice no more. Btw: It's just me, or does the video stops at 36 seconds?
They probably use Flash since its most widespread, has no compatibility issues (youtube should even work on some semi ancient flash player) and works on almost every os, including phones and portable devices, since it was made for the web from the start (unlike wmv or quicktime) personally I would vomit if they switched to wmv or quicktime.