To put it in perspective, eMarketer says marketers spent just $416 million on mobile ads in 2009—compared to the $22.7 billion spent across the web last year, according to the latest numbers from the Interactive Advertising Bureau. The other constraint about iAd is that it’s mostly a self-interested solution. It’s app-centric, and the majority of the mobile universe doesn’t use an iPhone and that won’t change anytime soon.

In his presentation earlier today, Jobs expressed a sentiment that even many mobile ad evangelists concede as well: “We think most of the mobile advertising really sucks. We thought we might be able to make some contributions.”

But the main contribution Jobs is talking about involves making the iPhone app experience a little less vexing. As Apple explains in its release, when users click on mobile ads, they’re almost always taken out of their app to a web browser, which loads the advertiser’s site. Most of the time, that process completely cuts users off from what they were originally doing in the app. So, iAd’s solution is to offer advertisers a full-screen video and interactive ad content without ever leaving the app, and letting users return to their app anytime they choose.

This actually does solve some important issues for marketers and agencies. For one thing, users might be more apt to click on an ad if it looks better and doesn’t force them to start over when they return to their app. Even more than PC-based online ads, mobile advertising has been particularly plagued by a stunning lack of creativity. A wider, and more interactive, canvas, could result in some more spending.

But the overarching problem is that no one can agree on what is the most important mobile ad metric to track, and the systems for measuring from analytics companies are still considered inadequate. There are so many companies offering competing metrics, no one can say which is the standard. To put it more simply, the TV ad market works because everyone agrees on the value of a Nielsen ratings point. That’s missing in online advertising, and is even more elusive with mobile.