The figures come from AdMob, one of the largest mobile advertising companies, who track which handsets and operating system hit their ads. Their figures show a trend of stagnation and decline for the iPhone, and a trend of growth for Android. Windows Mobile continues its decline into irrelevance, and the situation doesn't look very rosy for webOS and RIM either - but do note that these aren't sale figures; they're mobile web usage share figures.
Worldwide, it doesn't look so bad for Apple yet; it's still the king of the hill by a long shot, steady at about 50%. Android is making inroads, though, now accounting for almost a quarter of the world's mobile web usage.
And now we get to the interesting part: the United States. The top-notch Android phones have been available in the US for longer than in other countries, and carriers there have been pushing them longer. This shows: in the US, Android has almost overtaken the iPhone OS (which excludes the iPod Touch!) in mobile web usage - 42% vs. 44%.
In November 2009, the iPhone OS accounted for 55% of the mobile web usage in the US; now it's down to 44%. In the same timespan, Android grew from 27% to 42%. The US can be seen as a test bed for the rest of the world, since Android hasn't been pushed as much outside of the US as it has been inside of the US. In Apple's defence, though, the arrival of the iPad in the coming weeks may reverse the declining trend of the iPhone OS. And, as noted, the iPod Touch is not included in these figures.
All in all, it's clear that Android is no longer just a speck on the horizon. Google's mobile operating system is a serious threat to Apple's iPhone, which could further explain why Apple decided to sue HTC. Jobs might be drinking coffee with Schmidt in a nicely staged press moment, but in the meantime, the '80s and '90s are happening all over again for Apple: the PC business model beating the Mac one.