During November, 42% of the iPhone connections to AdMob's 6,000 advertising partners were over Wi-Fi, said the company in its most recent metrics report.

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

The iPhone, in fact, accounted for 51% of all wireless requests to AdMob's advertisers, while Apple's -- a music player with all the functionality of the iPhone except for its cell phone -- was responsible for 28% 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 Web sites," added AdMob's report.