In Turkey, most ATMs accept my extra-long PIN, but very few have UIs designed to fit more than 4 digits. On many of them, the digits will continue outside of the form field and sometimes all the way off the screen.
Strangely, there was one ATM that accepted 4 digits and then automatically continued to verification of the PIN. I never got a chance to enter the rest of the digits, but it still passed verification and allowed me to withdraw.
I had a 8 digit PIN, but only the first 4 mattered to the ATM. The screen would blink after the first 4 numbers, too, to help you notice you already had it.
Then two weird things:
1. The bank got bought by someone else, and the new bank demanded 6 digits. I had stopped using anything past the first 4, but they were still the first six from the original form I filled out years earlier.
2. They sent me my full PIN in the mail. At first I was surprised by this, since one-way-hash and all that jazz, but on reflection one-way hashing a six-digit PIN is pretty silly.
Is it a usability issue, or don't they realise that more digits means more pin options?