Did an experiment on the gold beggars on stormwind. They will auto-accept trades instantly, then i will cancel the trade immediately, spamming them with trade requests. After spamming trade and cancel a couple of times, they will target you and will autocancel all your trades instantly for a couple of minutes. I switched to another character and they are still stuck in auto-cancel for a couple of minutes. After doing this a couple of times, they will try to run away, hide and go AFK, still accepting trades. I find it funny that it still says thank you for a blank trade after I did this. They will eventually log out in fear of how stubborn humans can be. Did this for like a total of 10 minutes and it never came back. I have too much time in my hands.