Looking at AdMob's statistics, the HTC Dream, the first Android-based phone, generates 2% of their US requests and is now the fourth smartphone overall, behind the iPhone, BlackBerry Curve, and BlackBerry Pearl. It has also managed to capture 6% share of the smartphone OS market in the US.
Furthermore, AdMob's data shows that applications play a very important part in the growth of these two platforms. In March, over half of the total number of requests for both the HTC Dream as well as the iPhone came from applications.
Is Android growing fast enough? It's catching up with other competitors, but it's still far behind the iPhone. For example, Android traffic in the US grew an average of 47% per month in the first five months it was on the market; iPhone traffic grew 88% per month in its first five months. Yes, the pre-launch buzz and the help from Apple's marketing department were important factors in iPhone's stellar growth, but now that the buzz for both devices has somewhat quieted down, Android still has a lot of catching up to do.
There's an important difference between the iPhone and the Android platform, though, that might skew this ratio in the future: the iPhone platform consists of iPhone and the iPod Touch, while in time there will be many Android phones on the market instead of the handful we have now.
The entire AdMob Mobile Metrics report is available here.