A few blogs including Micropersuasion are pointing to a story by TV Week about the so-called iTunes effect. TV Week writes that the sale of videos on iTunes is boosting viewership of NBC's show "The Office."
I vote for a grain of salt in this analysis and I agree with TV Week's "to be sure" graph.
"Some experts urge caution in drawing a link between iTunes downloads and a show's ratings. ITunes distribution as a whole is simply not large enough to translate into a significant viewer increase on broadcast TV, said Adi Kishore, analyst with Yankee Group. 'We are not seeing the kind of volume yet on itunes that would show up in a ratings bump,' he said."
Another thing to take into account is that, even if iTunes is boosting reating, it could be simply thanks to the buzz effect around video online. And that effect could dwindle as as more video comes online.