Quick Tip: ‘Download’ YouTube (or like) Videos, Linux only
The video that you are currently viewing is on your Linux in a file: /tmp/FlashFOO (the FOO can be any random string. After the video is completely buffered, you just have to copy the file to your local disk for persistent storage. That is it.
You can watch as many you want and copy them too. Each of the Flash* files have a unique random character string.