In three months and two weeks, I've exactly two page requests from a Yahoo IP that were NOT "YahooCacheSystem".
These two page requests gathered all accompanying images and supporting CSS.
And yet, I've nearly 200 pages listed in Yahoo.
Thus, either Bing or Google is doing the crawling for Yahoo. I'm assuming the aforementioned.
Has anybody been able to confirm if there are particular IP's from one of these other SE's that are crawling on Yahoo's behalf?
