Interesting, but this could be HIGHLY misleading as well, especially if you're employing 'lack click' attribution.
Consider the scenario that Steve White wrote about in "The True Cost of Google Analytics"
"A customer first discovers your dealership via a third-party auto listing site. Then they come back to your site later by searching your dealer name on Google and clicking on an AdWords listing, which perhaps was right above a free Google organic listing for your website. By default, in Google Analytics, that AdWords click took 100% credit for that visitor, assuming as a fact that it was incredibly valuable, when it may have had no impact at all on whether or not that sale was made."
Where Steve says a third-party listing site, you could just as well say newspaper, or TV, or mailer, etc.
The point being you haven't determined who or what influenced the consumer, so you are no closer to determining a true ROI.
I see a tremendous benefit for Google, being able to claim credit for everything that happened before the click, but limited insight for the advertiser.
