DeeCee - 9:57 pm on Mar 5, 2012 (gmt 0)
The YahooCacheSystem does not even look at robots.txt.
I believe they do not look at it as a robot, since it is "merely" a caching system acting on behalf of another user. The user that is trying to hide.
My blocks for YahooCacheSystem is purely in denying them access. Though .htaccess or other methods. If their "customers" want my stuff, they can try to load directly and skip Yahoo's theft tool..
I would not even try to "talk" to them. They are like Google Preview, who does not care about such things either. (Except through blocking any and all snippets with 'nosnippet').