I don't know about making video downloads, but someone had mentioned that if you put a disclaimer saying that you don't own the characters would be helpful or maybe putting the video up in separate parts might do the trick as well. I notice quite a few SS videos I've seen on You Tube have parts 1 and part 2.
It's very possible that take downs of full length DVDs have something to do with the contract between the distributor and Sesame Workshop. Putting it up in parts - as I understand it anyway - just means it is less likely to be flagged by YouTube's automated content identification system. If the owner wants to go after it, they will.
It's important to remember that posting content you don't own is technically against the terms you agree to when you sign-up on YouTube.
In most cases, I believe YouTube tends to leave content in place if it is properly attributed so long as the copyright owner doesn't make an issue of it, but contrary to what a lot of YouTubers believe, disclaimers don't really mean anything. People often upload copyrighted content to YouTube with a disclaimer saying something like "no copyright infringement intended" but that does not change the fact that
it is copyright infringement.
Likewise, people often post this on full-length episodes of TV shows:
Copyright Disclaimer Under Section 107 of the Copyright Act 1976, allowance is made for fair use for purposes such as criticism, comment, news reporting, teaching, scholarship, and research. Fair use is a use permitted by copyright statute that might otherwise be infringing. Non-profit, educational or personal use tips the balance in favor of fair use.
...which sounds fantastic, except that posting all or (in most cases) even an extended portion of a TV show doesn't even come close to being fair use.
All in all, I think Sesame Workshop is pretty cool and progressive when it comes to online videos, both sharing them on their official channel and allowing fans to post their own.