Is Google cloak-checking me?

Or am I getting paranoid?

[Doofus]

Google crawls dynamic pages on my site. Yesterday, several days after this latest crawl stopped, I get "spot checked" by Google IPs that don't reverse-resolve. This one was 216.239.35.4 (I understand Google has everything from 216.239.32.* through 216.239.47.*).

The thing is, their behavior is really weird. They will spot check one or two pages only, at various times. Each of these they hit a half dozen times. What concerns me is that under some conditions, the data returned for those pages will not be as complete, depending on various conditions, as what they got during the regular crawl.

I'm now letting all their Class C's through, so that there won't be any differences between checked and cached pages.

Is this a possible "cloak check"? Does anyone have information on which IPs at Google are used by machines and which are used by humans?

Maybe my content is really interesting, and some Google employee is improving his mind and I shouldn't be concerned!

[littleman]

I believe google actually has 216.239.32.0 through 216.239.63.255.
I've been particularly examining 216.239.35.4, it is sometimes used for Google WAP proxies and sometimes it is using a browser UA. I never see it with a referrer.