Yeah, I'm happy enough just closing any tab that starts sprouting unsolicited audio, either from ads or actual content that autoplays. Unfortunately, I doubt most web analytics do a good job showing people leaving their site in droves once some autoplay content starts.
Slashdot might be a good example of this, though... I used to leave /. running in a tab all day long, but now I usually end up closing it after something autoplays nowadays and not going back. Maybe someone noticed, because I do see autoplay junk hit the page slightly less often now.
Facebook oddly enough actually has a pretty nice system where videos autoplay muted as you scroll by them, pause once they're offscreen, unless you unmute or hit play. It would be nice to be able to give better reasons for blocking content, though, like "This link was a useless slideshow" or "The page had some stupid autoplay thing"