My bank (in Germany) just recently introduced a feature on their ATMs that allows you to easily change your PIN. I think it's pretty obvious that's a bad idea,

My bank (in Germany) just recently introduced a feature on their ATMs that allows you to easily change your PIN. I think it's pretty obvious that's a bad idea, given all the huge posters also hanging everywhere in the bank, sternly warning people not to pick a dumb PIN. I'm sure that'll work. 4-digit PINs are easy to remember. It's real simple to always come up with some sort of mnemonic. There is no need whatsoever to pick your own.