That is a good point. Is the image highly sexual? Are their children in the image?

Not a perfect CP detection system (might detect kids playing in a room with a rated R movie playing on a TV in the background), but it would be a good first attempt filter.

Of course, if you upload a lot of files to Google Drive and run a sanity check like this on the files, it is too late to save you from Google.

Avoiding putting anything with any risk potential on Google Drive seems like an important precaution regarding the growing tyranny of automated and irreversible judge & juries.