I stumbled across something related to this a while back, couldn't find the same video as before but here is this:
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.
This was off a video featuring a "main stream" song and has been up since 2007. From what I gather he had his video flagged but came back added the disclaimer in his info section and then also added the song's name and who sang it into the video in the intro.