The HTC Evo has already crept up on the Nexus One when it comes to Android handset market share, though it has a long way to go before it becomes the dominant Android handset. That's according to mobile advertising firm Chitika, which gathered data on 821,201 of its ad impressions for the first two weeks of June.

Chitika says that the HTC Evo has already grabbed 1.93 percent of the mobile ad market, nearly matching the 2 percent held by the Nexus One. Considering that the Nexus One has been available to users since January and the HTC Evo only launched on June 4, it certainly looks as if users have taken significantly more interest in the Evo. Part of the reason may be the marketing push behind the two phones—at least anecdotally, it seems as if I'm bombarded with more ads for the Evo outside of the Internet than I have ever seen for the Nexus One.

The most dominant Android handset was the Motorola Droid, which made up 33.75 percent of the mobile ad market. This is no surprise, as the Droid had some of the most aggressive (and clearly effective) marketing of any Android-based phone to date. The HTC Hero and HTC Droid Eris came in second and third with 9.9 and 8.2 percent respectively.

A full 8.13 percent of Android-based phones were unidentifiable: "[T]rue to Android’s open-source and incredibly diverse nature, some 8% of the operating system’s traffic in the sample was from unrecognizable devices or devices with extremely low usage," wrote Chitika. A smattering of others took up the rest of the pie.

As for carriers, it's clear which one (in the US at least) that Android users prefer: nearly half were on Verizon compared to only one percent on AT&T. There was a larger group of Android phone users on "N/A" than on AT&T, according to Chitika's data, making us wonder whether a similar trend might happen one day if and when Apple decides to roll out a CDMA version of the iPhone.