To download videos from Facebook, YouTube, or *any* other site that contains video or any other kind of media like images or music, the Video Download Helper add-on for firefox is a must. You can get it at https://addons.mozilla.org/en-US/firefox/addon/3006. Once you load it it adds an icon to your tool bar. When you are surfing the web if it finds content that it can download, like videos or music, the toolbar button gets animated. You can then select which pieces of content you want to download directly to your computer. This is easily the fastest way to download video from Facebook.