The user ultimately needs to retain control. And I'm especially interested in the exception for audio - that really should be user-controllable, otherwise it just encourages annoying page authors to be even more annoying.
The audio thing works because there is an obvious icon in the tab bar that shows the source of audio, so if developers use it in an annoying way the user can easily respond appropriately.
There is now an incentive to do this, so it will happen. Same as "with popup blockers everywhere, popups are now replaced with HTML5 above-content layers."
The user ultimately needs to retain control. And I'm especially interested in the exception for audio - that really should be user-controllable, otherwise it just encourages annoying page authors to be even more annoying.