Discarding misdirected mail is a felony (18 U.S. Code § 1702). For example, you receive a flyer in the mail addressed to John Smith who previously lived at your address. If it doesn't say "John Smith OR current resident" then discarding that junk mail is a felony. You are supposed to write "Return to sender" on every piece of junk mail or correspondence not addressed to you and put it in the outgoing mail. People discard junk flyers every single day without looking at the address first. Simple things like that.

To tie back into the original discussion on HIPAA, I had a collection agency sending mail addressed to a previous resident to my address once. The return address was the clinic of the patient. I was dutifully writing RTS on every letter and putting it back in the mail, but they would not take me off their nastygram list. That was until I wrote "You know, it's a felony HIPAA violation to be leaking this patient's name and clinic to me after you've been notified of the incorrect address." The collection letters immediately stopped after I did that.