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Google’s ‘Secret’ Update Scans All Your Photos
(www.forbes.com)
This is a most excellent place for technology news and articles.
The official reason they dropped it is because there were security concerns. The more likely reason was the massive outcry that occurs when Apple does these questionable things. Crickets when it's Google.
The feature was re-added as a child safety feature called "Comminication Saftey" that is optional on a child accounts that will automatically block nudity sent to children.