Earlier today, Erick Schonfeld over at Techcrunch wrote up a release from AdMob disclosing Smartphone OS marketshare (measured by impressions). In their report, Admob showed that a monstrous 55% of all smartphone requests came from devices on the iPhone OS, while Android made up 20% and RIM a measly 12%.

Interestingly, earlier today Sean P. Aune posted his regular Mobile Monday report that included data from the SMART report released every month from one of our sponsors Millennial Media, which contained some starkly contrasting data.

In the Millennial Media report, they showed that the iPhone consists of only 33% of monthly impressions, RIM following closely at 31%, and Android at a measly 8%.

We got a short missive from Millinnial this morning, and they said that internal reports they’ve received from Comscore back up this data, as does Nielsen.  We’ve put in calls to both analysis firms to confirm and are awaiting reports of verification (which we may not get until tomorrow), but given the old data I’ve reviewed on the web, the Millennial numbers certainly seem more plausible.

If you look at this Comscore data from May of this year, it tells a similar story to what Millennial is claiming.

They show RIM with the greatest marketshare, at 38%, Windows with 27%, and Android and iPhone at 2% and 21% respectively.

Certainly things have shifted since then, but for iPhone to explode to 55% past all competitors since then would be truly remarkable.

Hopefully the third parties will respond soon and give us some illumination on this disparity. Right now, AdMob looks like the odd man out on their statistical data, but we’ll see when the numbers come in.