A few days ago, the Jensense blog reported that ads for Google Adsense are running on the Yahoo Publishers Network, urging viewers to “Make Money on the Web with Google”.

While the MarketingLoop blog speculates that perhaps Google was running a campaign to gain intelligence on Yahoo’s operation, this seems unlikely - it would be far easier to perform such a study with a third-party campaign less likely to attract attention.

It’s not surprising that Google would seek to run ads wherever it can. It’s perhaps a bit more surprising that Yahoo would accept an ad from a direct competitor to the very service running the ad. Did a Yahoo ad salesperson have a target he couldn’t hit without signing Google? Did a Google prankster figure out how to sneak the ads into the Yahoo system? Or is this part of some kind of mutual non-aggession pact which will end up showing YPN ads on Adsense sites as well? Maybe Yahoo is following the standard advice for publishers: keep your blocked URLs to a minimum to maximze your revenue.

In the grand scheme of contextual advertising, perhaps it’s nothing more than an amusing story and screenshot to be saved for future chuckles.