More than 40 percent of all US traffic last month between Appl's iPhone and AdMob, the world's largest mobile ad network used WiFi connections, not over AT&T's cellular data network.

iPhone users' heavy reliance on wireless is part of a growing trend, according to the report. "In the US, 8 percent of total requests in November were on Wi-Fi networks, up from 3 percent in August. [The] 42 percent of iPhone requests made on Wi-Fi networks [is] notably higher than most other Wi-Fi capable phones, which average between 10-20 percent."

The iPhone, in fact, accounted for 51 percent of all wireless requests to AdMob's advertisers, while Apple's iPod Touch - a music player with all the functionality of the iPhone except for its cell phone - was responsible for 28 percent of all wireless requests. Because the iPod Touch lacks a connection to a mobile carrier's data network, all of its Web traffic is conducted over Wi-Fi.

"iPhone Wi-Fi usage is generally higher on iPhone specific sites and applications than on normal mobile websites," added AdMob's report.

The iPhone's reliance on wireless backs up the thinking of analysts who see the device as Apple's defacto "netbook," the term given to the small, lightweight and low-priced notebooks that have been selling well because of the recession.

During an October conference call with Wall Street analysts, Apple CEO Steve Jobs essentially dubbed the iPhone, and its iPod Touch sibling, the company's current netbook . "One of our entrants into that category, if you will, is the iPhone for browsing the Internet and doing e-mail and all the other things that a netbook lets you do," Jobs said at the time. "Being connected via the cellular net wherever you are, an iPhone is a pretty good solution for that, and it fits in your pocket."

Analyst Ezra Gottheil of Technology Business Research agreed at the time, and today said that AdMob's numbers reinforced that view. "For sure, it's yet another piece of evidence to support the idea of the web in your pocket - something that doesn't have to be in a carrying case, boots fast or is always on. That's a very handy thing to have."
The browser, after all, Gottheil continued, "is not just something that's inside your computer, it's the reason why you have a computer. So if you can run it on something else that's more convenient, you will."

AdMob also noted that total iPhone requests - over both mobile networks and Wi-Fi - to its partners jumped by 52 percent in November compared to the month before. The iPhone accounted for 6.3 percent of all requests during the month, leading any other individual handset by a wide margin.

As a handset manufacturer, however, Apple accounted for only 7.8 percent of all requests, putting it in fifth place behind Nokia, Motorola , Sony Ericsson and Samsung. Nokia's handsets collectively held 31.9 percent of the AdMob share, for instance, while Motorola accounted for 12.7 percent.

Research in Motion Ltd., the maker of the BlackBerry line of smart phones, was seventh on AdMob's list, with a 3.9 percent share in November.

AdMob's November report can be downloaded from the company's Web site (download PDF) .