I keep getting bugs in my ear (or little birdies) dropping hints that Yahoo!'s organic search is predisposed against websites serving AdSense. That' s not to say that many sites serving the Google ads don't rank well at Yahoo!, but rather that Yahoo! has some negative associations with AdSense serving content and won't be as friendly as they should be.

I've heard this rumor two ways now - first (which I find less credible) is that the ranking algorithm at Yahoo! is biased (pushing AdSense content lower than it would be ordinarily). And second (which fits with some experience and seems the more likely of the two), is that Yahoo!'s Slurp won't crawl (or won't index) as much content as they would/should/could on large content sites serving AdSense.

Is there any truth to the rumors? My guess is that we'll never know for sure; but, it sure makes for high quality industry gossip... Your thoughts?