Mailman marked my package with two clacks as delivered online.   Ran to locked mailbox, nothing in it.  See the truck down the street, and see him throwing a bubble mailer back into his truck.  Sprint and catch up. 
"Hey, did you forget to put something in Apartment X at Y address?  I got a notification and it isn't there"
"Uh nope, don't know, there wasn't a package for there"
"It should be a bubble mailer.  With insurance.  Kinda like that one there on the dash" *points*
"Oh um... yeah.  Is this your address?"
"...Yes.  Here's my ID, let me have my package."
And that is how I almost got clack-jacked.
PS.  Sorry if this is the wrong thread (ie not clack therapy), but I was pretty stunned to have that happen to a package.  Watch yo clacks!