AdMob today offers up some new insights to the mobile space. The company reports on a small sampling of the handset market by tracking device usage through the AdMob advertising network. It’s not an exact representation of the market by any means, but it gives us a glimpse at trends. You can see the latest PDF report here.

One focus from the reports is the growing usage of WiFi for mobile browsing due to the Apple iPod Touch. But perhaps the bigger news is what AdMob found about the Android platform. With just a single model out, the young T-Mobile G1 shows a 50% jump in market share in the U.S. for the month of January. Again, this is strictly a small sampling on one advertiser’s network, but I find it impressive regardless.

In December, Android reportedly had a 2% share and January saw the platform move to 3%. It’s certainly easier from a mathematical standpoint to show high percentage growth when just starting out, so I’m curious how the trend plays out over the next several months. Maybe that makes the “fastest growing smartphone platform” claim a little dubious, so here’s more AdMob data to sift through.

In November, the T-Mobile G1 running Android didn’t make AdMob’s top 20 handsets list. Heck, there were more web requests over WiFi on the Sony PlayStation Portable (No. 18 out of 20) than on Android handsets that month. That actually makes sense, since the device had just hit the market in mid-October.

December brought change to the AdMob metrics: Sony’s PSP dropped from the list but Android handsets still didn’t crack the top 20. However, recent January numbers show that the HTC Dream Android phone arrived to the list. Ironically, it occupied the same No. 18 position as the PSP once held and according to AdMob tracking, accounted for 0.9% of the smartphone market in the United States. Not a huge grab, but surely better than a no-show.

Numbers aside, what factors might be contributing to to Android’s noticeable growth?

• The G1 handset is widely considered T-Mobile’s flagship device, and basically their only 3G smartphone. Is it getting pushed harder in stores as a result? T-Mobile needs to recoup costs from their 3G network investments somehow.
• With dreams of riches from an application store and the anticipation of paid apps in the Android market as early as this week, some developers have to be interested in the handset. Back in December, Google began to offer a SIM-unlocked version of the G1 to developers at $399 which could be adding to Android’s share of the market.
• Another bonus to Android’s growth could be Google’s employee bonus; Literally. Instead of more stock options or financial benefits, Google took a different approach in this challenging economy. Each Google employee received a free Android handset for their yearly bonus.

Since we have plenty of readers smarter than me, let me pose the question. Do you think that the Android platform is beginning to make noticeable inroads in the market? What else might be driving such a trend? Or is the trend not a trend at all: are the recent AdMob percentages simply overstated because we’re dealing with such a small number to begin with for Android?