I'm not sure I agree, Carl.

"Napstering an MP3" was/is unethical because it was/is consuming and distributing someone else's (the artist's) commercially available product without their consent.

YouTube videos are a lot more gray. A lot of video content is shared freely with no profit motive at all by its creators. Think "how to" videos, etc.

Appropriating and aggregating this third-party content and forcing others to watch advertising in order to generate revenue from something YouTube didn't create is what seems unethical to me.