Mike sent a picture of his passport through email, and two seconds after he sent it, he got an email from Google listing products that are similar to his passport. He's concerned that the information is out there somewhere now.
Leo says no, it isn't. Google, and any other email provider for that matter, scan through user emails to look for spam to block and to display contextual ads. It's not likely that Google actually scanned his passport image, but probably just the text in the email which contained the word "passport". This is really nothing to worry about, they're not keeping his emails and they aren't even being read by humans.