iPod ratings?

Paid Content is reporting, from a tv week article I can't access, that the NBC show The Office is reporting it's largest rating share, and is attributing that boost to their sale of episodes on iTunes. Here's the gist:

NBC's show "The Office" delivered a 5.1, its highest ratings ever-last Thursday among adults 18 to 49, a bump the network credits in large part to the show's popularity as an iPod/iTunes download. The series is NBC's top-performing video podcast available on Apple's iTunes, where it has been available since Dec. 6.
"The Office" has accounted for one-third of all the NBCU downloads on iTunes...
There's no foolproof way to know if that really was the case, but it really is eliminating all other factors..

It will be interesting to see how this plays with a larger sample size - considering that more and more shows are being made available via iTunes, I think we'll have some perspective on this soon enough...

UPDATE: Here is the link to the TV Week article.