My friend just told me today about her experience. She made an advent calendar for her grandkids who live 60 miles away, she wanted them to have it by Dec 1 so she mailed it the week before via priority mail. She watched the tracking - it went from her town, to their town, back to her town, back to their town, back to her town. She went to her post office to see if she could catch it before it bounced again, since she was planning on visiting them on Dec 5th. The package was a long, narrow one, with her address at one end and the grandkids' address at the other. When she originally mailed it at the post office, the clerk had stuck the priority mail sticker near her address, and apparently the mailman who delivered on the grandkids' route thought that meant her address was the delivery address, so he kept sending it back. The scanning software knew better, so every time the package hit the main sorting hub in Portland, it would send it back south 60 miles to the grandkids!
Apparently the mailman on the grandkids route never scratched his head and wondered why that package kept coming back....