The question is, how do you know if one of these evaluators are on your site, sniffing things out?
A WebmasterWorld thread suspects that the Google evaluators come from cart.corp.google.com. In fact, WebmasterWorld administrator said he always sees the "first parameter" string along with a "?cmd=review." To him, this implies it is an evaluator.
Should you worry if you see this in your log files? Depends, are you doing anything shady or borderline?
Forum discussion at WebmasterWorld.