A former user of Google's AdSense - a publisher with the nom de plume "Kurtpdx" - has caused some ripples by alleging that Google's pricing system penalizes publishers who have even one low-performing site by lowering the ad prices of all sites in the publisher's account, writes MediaPost. Kurtpdx says an AdSense representative told him that's how it works, in an attempt to entice him back to AdSense after he switched to Yahoo Publisher Network.

Riled at the implication that publishers should remove low-performing sites from AdSense to get higher prices on their other sites, publishers expressed their pique on JenSense.com, where Kurtpdx's post was publicized.

Google on Friday posted a response on the AdSense blog: "More than conversion rate goes into determining the price of an ad: the advertiser's bid, the quality of the ad, the other ads competing for the space, the start or end of an ad campaign, and other advertiser fluctuations."

Jupiter Research Analyst Gary Stein said Yahoo has found a chink in Google's armor: "The way you compete against Google for B2B accounts is to say, 'Well, we're willing to share with you information: We're more responsive, it's not a black box here'."