Multitasking on the iPhone and iPad is a nice addition to the platform, but I think the jaw-dropper at Apple's news event this morning was the mobile ad platform called iAd that Steve Jobs unveiled.

Both additions were expected but the ambition and scope of iAd was surprising.

It's a huge potential market for the company if users accept the advertising that may soon be woven deeply into their Apple devices.

"The average user spends over 30 minutes every day using apps on their phone," Jobs said, according to Engadget's live blog at the event. "If we said we wanted to put an ad up every 3 minutes, that's 10 ads per device per day. That would be 1 billion ad opportunities per day."

Users may benefit from more free apps supported by ads. Maybe that will offset any resentment about immersive ads on a mobile device for which they pay monthly fees to use, and temper app price escalation that came with the iPad.

Apple's going to take 40 percent of the revenue from iAds that it's going to sell and host. In response to a question, Jobs said developers can use other ad systems besides iAd, according to the Wall Street Journal's coverage of the event.

I wonder how it's going to work to have multiple systems feeding ads into the apps. Will other ad systems have the same access the new ad serving and display capabilities Apple's building into the operating system without paying the 40 percent?