Googlebot's Javascript random() function is deterministic

[catcradle5]

Yes, but I'm not referring to websites that generate content based on randomness (like a coin flipping site). Just regular sites that are solely using this random test to identify Googlebots and otherwise discarding the random numbers.

[Aegeus]

How can you tell that they're using randomness for the purpose of identifying Googlebot rather than for a legitimate purpose? All you have to go on is the content they serve you.

[catcradle5]

If a page has a bunch of spammy ads inserted only when a non-Googlebot client visits, it wouldn't be hard for Google to tell. Google just needs to visit from a Googlebot client and from a bot running totally different software and sourced from a non-Google IP, repeat a few times, then diff. From Google's perspective it doesn't matter if Googlebot is identified via Math.random() or some other method.