Why are folks so interested in Apple's ad inventory?

It has the potential to be more valuable than inventory on many phones.

Why?

People who own smartphone devices are more active on their cell phones than your typical cell phone owner. For simpler tasks like SMS, they are moderately more active. For more complex tasks such as shopping, using maps, banking or doing product research they are significantly more active. iPhone users are some of the most active smartphone users when it comes to commerce-related activities.

Advertisers have held back on spending more on mobile marketing for many reasons. One of the primary reasons has been their inability to demonstrate the effectiveness of the medium or calculate an ROI. It gets a lot easier to calculate the ROI when consumers are buying items or using services such has mobile banking to deposit checks. Consumers are spending real money. My colleague Sucharita Mulpuru will be working on a mobile commerce forecast later this year. Anecdotally, we saw consumers spend in the hundreds of thousands of dollars with individual merchants/hotels/restaurants in 2009. We're likely to see run rates in the low millions for a few companies within a few industries by the end of this year.

The more consumers spend, the more advertisers will be motivated to spend. Consumer product and service companies will invest in mobile services such as "find the nearest," consumer reviews, available inventory, etc. to support commerce-related activities. The greater the supply of services (of great services), the more adoption and usage we'll see among consumers. Then consumers will spend more because the experiences will be convenient - it'll be easy to buy books or toothpaste.

iPhone owners are some of the most likely candidates. They are already buying content and applications. I think they'll also buy products and use services. Total spend is small today relative to online or in physical stores, but it is positioned well to grow this year and going forward.

And what else? The targeting ... every content and application download and purchase is tracked by iTunes. iPhones have GPS. How much of this will Apple make available to the developer community or advertisers to enhance targeting?