[kleiba]

In situations where you have a textfield "enter password" and another textfield "re-enter password", it would probably make sense to prevent pasting into the second field iff you didn't paste into the first field.

Better yet, if you pasted it into the first field, the second field should become disabled.

This is because usually password fields are not in clear-text but display stars for letters, so you don't know if you accidentally mistyped the password. But if you pasted it in in the first field already, there's no reason you should have to paste it a second time.