9 seconds of page load for ads is unacceptable. Mobile browsing has become a pita because of all those poor ads network, and i think once again (after the flash controversy) apple is going to save the web by making radical decisions like this one. It may very well be that mobile web content browsing becomes even more pleasant than using native apps thanks to that, since they too seem to fall for the trend of putting…
Apple isn't doing this to save the web, they are doing this so developers will be forced to create a native app to show ads and make some money. Easiest way to show ads in a native app on iOS... oh wouldn't that be iAd service in which Apple gets a cut of the profit?
The WWDC session for this feature specifically highlights a major privacy issue this can help solve: blocking privacy-invading tracking scripts.
It's completely possible to show ads without tracking every move the user makes across the web.