Why would Google - or any other company for that matter - spend time and money on something as complicated and error-prone like that? They would never be able to sell it to anyone and it could ruin their brand substantially if it ever came out.
I don't see why you would even consider this to be happening.
> Why would Google - or any other company for that matter - spend time and money on something as complicated and error-prone like that?
This is a problem of technology. These tend to go away over time (e.g. Youtube's automatic copyrighted content detection). Bottom line is that the ethics and policies of the underlying company make me question the privacy of my data from the get-go.
I don't see why you would even consider this to be happening.