They may have been refering to embedded Youtube being a hog in that people will often post a URL to your site that has the embedded youtube link. The Youtube video doesn't hit your bandwidth, but google searches and links to you site that have the embedded youtube vid will.
I am actually guilty of this myself. I have found a few good embedded vids here, and instead of clicking on them to go to youtube to get the URL, I simply cut/paste the URL for the forum and IM/Email them to friends. This type of activity is double edged: It steals a little of BYOAC's bandwidth (in my example) but at the same time it exposes people to the site.