Jason Calacanis has noticed a sudden uptick in the click-through revenues for the Google ads he runs on his Weblogs Inc. blog network, and he wonders if this isn't the first real evidence of the coming battle with Yahoo over contextual ads. Calacanis is not alone. A couple of other publishers have told us they've seen the same thing with their Google ad revenues. Has Google boosted the split of the ad revenue it gives publishers that carry its ads - a tweak intended to undermine the success of Yahoo's new, AdSense competitor?

Alas, the truth appears not to be so intruiging, at least according to Google. Google won't talk about how it splits its AdSense revenue with publishers. Publishers themselves don't even know how big a cut of the ad dollars they are getting. But a Google rep did tell us this afternoon that it has not tweaked the revenue split. What publishers probably are seeing, he said, is the effect of a new AdSense feature intended to boost ad revenues. Launched in the past few days, the feature analyzes which ads are performing best on a page. If a single ad is outperforming a block of four ads, Google will dump the other three ads and stretch out the lone, high-performing ad across the same space. The result is an uncommonly large Google ad that, hopefully, generates more revenue.

The new feature launched last Friday. To see it action, go to the Wireless Weblog and look at the Google ads that run below the first blog post. Multiple page refreshes should reveal a few of the jumbo-sized ads.

Is that really enough of a change to drive the kind of revenue lift that Calacanis and others are seeing?

The bigger issue that continues to frustrate many publishers is the black box of secrecy that surrounds the revenue split. Yahoo tells us that, as part of the testing of its new ad program, it's considering giving publishers more information about how revenues are shared with Yahoo - maybe a range of percentages. Would that satisfy the curiosity of publishers? We'll see.