The personally-identifiable bit could be a watermark: slight coloration changes. It could also be the last-updated time, or particular numbers in a column... w

The personally-identifiable bit could be a watermark: slight coloration changes. It could also be the last-updated time, or particular numbers in a column... which would have only been served to a single account in a logged transaction. A company that cares about its proprietary information can easily log and/or watermark everything served via internal tools.