The iPhone has access to that high-speed 3G network. But admit it: you use Wi-Fi whenever you can, right? It’s easy and simple to use. Many are tempted to walk into every Starbucks they pass and log in for free Wi-Fi just because you can. 3G may beat EDGE, but Wi-Fi beats both.

Turns out we’re not alone. According to a report released by mobile ad network AdMob, iPhone users divide their time almost evenly between cellular and Wi-Fi-based networks, where it was once believed cellular networks were dominant.

AdMob is the company that makes it easy for Web sites and iPhone apps to embed ads into content. As a result, it’s able to monitor where incoming requests for ads are coming from: via a cellular provider’s digital network or via other IP addresses which are presumably part of a local Wi-Fi network.

AdMob says iPhones made 58 percent of their ad requests from cellular networks, with the remaining 42 percent being made on Wi-Fi networks, a much higher number than previously thought.

In comparison, the total number of Wi-Fi based ad requests on AdMob’s entire network was only eight percent. Between the iPhone and the Wi-Fi-only iPod touch, Apple devices made up 79 percent of all Wi-Fi requests AdMob saw in November, which is a huge number.