netmeg - 8:01 pm on Aug 14, 2011 (gmt 0)
I just looked; I have a ton of "network unreachable" errors for two sites, August 10-12, and a handful of "robots.txt unreachable" errors for the same dates. I see no dip in my stats for those two sites, plus they're hosted (with a third, larger site) on extremely reliable hosting - plus the third site doesn't report any errors at all.
I think it's gotta be Google. Also seeing lots of 404 errors for stuff that appears to come up just fine.