lucy24 - 2:52 am on Nov 26, 2012 (gmt 0)
fwiw: I can't be bothered to keep track, so I just block 'em by name:
BrowserMatch Yahoo keep_out
pretty well covers it ;)
This probably dates back to last January when I looked closely at robotic behavior and ended up tossing several into the "because I don't like your face" bin.