I have long been aware that there were different telephone keypad layouts that put letters on different number buttons, but it was only this past week that I really started researching this topic in detail.
The most amazing thing I have discovered is that while the most common layout on phones is an international standard (ITU-T E.161), the other most common numeric keypad (aside from calculators), the PIN pad found on ATM machines and other banking devices, typically puts the letters Q and Z on the number 1 button.
Why this came to be is beyond me, since I have been able to find no specification that places Q and Z on the 1 button. And the current European ATM standards I have found quite clearly specify the ITU-T E.161 layout. This of course means that as more people do banking on their mobile phones in addition to ATMs, anyone that uses a Q or Z in their PIN will have difficulty switching between devices.
Aside from there being no published standard that places Q and Z on the 1 button, there is no good reason to put these letters anywhere but where E.161 specifies. The Predecessor of the ITU-T standards group researched this in 1991, with the result showing that people preferred Q and Z on the 7 and 9 keys by over 83%.