Google offers a way to get content you have from the Google servers. The most recent addition to this service allows a way to download YouTube content. Here is a ReadWriteWeb post on the service. I gave it a try and it worked perfectly – three gigs of content I immediately deleted. I understand the motive to have control over your own content, but when you get down to it, I trust Google storage over my own. You may have a reason other than backup to secure your material.