Youtube has a section which is called Test Tube that has some of the more experimental aspects of the website.
Out of the features you can dick around with, the video editor is actually a really good feature and to be honest, it was only a matter of time before they would add such a feature to a video site. I can’t believe video websites prior to youtube didn’t think of this before now. I guess it is just easier to host to video and have people use their own software than to try and do it online. But now that there is a lot of focus on cloud computing that doing all your tasks on the net just makes sense.