I want ask if it si possible to make some protection , so that is´nt possible to extract the video URL from source code, and than download this video.

For example:
This is part of source code of my site, which can see everyone:

<script type="text/javascript">
var so = new SWFObject("http://www..../player/player.swf","vshare_player","425","350","8");
so.addParam("allowfullscreen","true");
so.addVariable("file","http://www...../flvideo/1212438906371020886.flv");
.
.
.


Is no problem to copy the url of the video and download it.
How to prevent this?