AdMob announced today that they have reached the milestone of serving more than one billion ads per month. Wow! Over 500 million of these ads alone are served up in the US.
Granted, those are not any near our online numbers, but it's an impressive milestone. By our estimates, only a minority of cell phone owners browse the web on their phone (though certainly more will do so with handsets like the iPhone and the N95 from Nokia), and a small percentage of those do so frequently (i.e., daily/weekly). Monthly per user page views on cell phones don't add up to daily numbers for most of us.
It's an impressive number. It's also impressive to see the growth that ad networks like Admob and Third Screen are experiencing. I think lack of inventory has been one of the primary inhibitors to growth of mobile display ads. This will continue to be an exciting space to watch.