“Previously, you were charged the same for traffic from all web sites within our distribution network,” Yahoo said. “Now, with quality-based pricing, you may be charged less for certain clicks than you otherwise would pay, depending on the overall quality of the traffic provided by our distribution partners.”

Yahoo will measure quality based on conversion rates and what they described as “other measurements” of the traffic coming to advertisers from partner sites. Barry Schwartz at Search Engine Land said implementation type will be one of those other measurements.

What’s great for advertisers won’t be so wonderful for publishers. Jen Slegg pointed out at JenSense that the people who bailed out of Google AdSense when smart pricing impacted their revenues will see a similar situation with Yahoo.

“So Yahoo could discount publishers for specific traffic sources, whether it be from spammy third tier engines or theoretically even taking a competitive stance against Google or MSN traffic while boosting Yahoo referred traffic,” she wrote.