Hi Skylark,
For strictly educational purposes there is generally not a problem. However, this is a grey area as youtube videos may have been ripped from commercially available DVDs, etc. At our discretion if we feel that approving your files may be stepping on other publishers' and developers' toes, we may reject the file, and of course any content that is not free of copyright cannot be considered for premium status.
Hope that clears things up!
Shuki