Underscore In Da House

Eric and Tom on iMediaEric and I dominate iMedia today, with his article on impression discrepancies and mine on the PayPerPost kerfuffle.  Underscore in Da House! Shouldn't be long before the PayPerPosties start writing stuff in response.

Eric gives some good tips on how smaller agencies can get involved in figuring out how to deal with impression reporting discrepancies.  Right now, we're using our agency-side server numbers until we can figure out a way to get 100% of the buys tracking closely enough with publishing-side ad servers.  I think a lot of agencies are doing the same.  What's perplexing to me is that if the counting methodologies are the same, what's the biggest driver behind the differences in impression totals?  I've heard all sorts of implausible theories over the years - spiders and robots (doubtful - both servers should be filtering out the IAB's list), people who double-click instead of single-clicking on ads (still doubtful, the numbers are too far off), bailouts in between calls between publisher and agency servers (10 percent in that few milliseconds?  I doubt it.) and all sorts of other stuff.