Keepvid is a useful site. It provides for a way to download videos from YouTube, Google and a variety of other sites it lists. Just mention the URL in the text box, select the site from the list, and click Download. When the text in the text box disappears, look under the text box for a >> Download << and you know what to do from there on! If you don't know CLICK! .... and check you head to know if you are a total retard! (Sorry too much George Carlin!)
If you are from some kind of a cyber law enforcement agency, all I have to say "Don't shoot the messenger!"