The relevant practice you're describing is leeching and the immediate connotation is inappropriately as harsh as the term "junk bond".
Your conceptual description is accurate but YouTube's content is leechable, sites like HuLu, even CSpan go to greater lengths to protect their content by instructing your browser to cache the content in your systems RAM instead of the disk even overriding your browsers preferences. Other measures such as storing the content in an encrypted manner that requires a rapidly expiring cookie for deciphering along with layers of redirection on the server side that strives to isolate your system from directly accessing the content which is being proxied from internal media servers to the web server, then you.
YouTube employs those measures for the premium content like day pass $9 movies but the never ending competition between the content providers and the labeled pirates keeps prevents the topic from becoming stale.
Whether you can access the actual source FLV, MP4, etc files or have to rely on sniffing the content with a purpose built packet sniifer (even VLc and RealPlayer has mechanisms to record the stream as analogous as a VCR), isolating content from unapproved capture is impossible.
I love the wording of your question because it has all of the hallmarks of a SecPro with more of a traditional background in law enforcement, policy auditing and it seems like the earnest curiosity of someone on the quest to learn more and that is becoming rarer in this profession.
If you google for "leeching tools" you'll get a Chicago thick phonebook of results and just starting with FlashGot or FlashVideoDownloader as FireFox add on's will demonstrate the semi obfuscated URL's. If you hate FireFox and prefer IE, you can use the ANT Downloader, it's FF and IE compatible.
My own experiences, I've found Firefox addon's more capable for this leeching in its depth and breadth of choices, while Chrome seems to be lacking especially when trying to leech video from YouTube or any other site in the google family.