The only scenario I can accept paste-blocking is double-field password creation. At least one should refuse paste, just to make sure I haven't copied the wrong string.
Whilst we're on the topic: I hate stupid input fields that don't ignore whitespace and have a maximum number of characters. So you paste the space-separated number (I'm looking at you IBAN), get an exception because of the spaces, go back and remove them, get another exception, and then realise that the number was truncated due to the field length restriction applied on paste. ARGHHHHHH
>At least one should refuse paste, just to make sure I haven't copied the wrong string.
I disagree with this. If you paste a password into both fields, then paste it into your password manager, it doesn't matter if you've copied the wrong thing, because your password manager will still remember it.
I think it's a combination the "Justification 3" in the article (having passwords stick around in the clipboard could be an issue) and maybe the idea by some people that passwords should be memorized and never written down anywhere.
Maybe they're worried people will have a "password.txt" in My Documents where they store all their passwords in cleartext. That being said it'd still probably would be more secure than having the same password everywhere like most people seem to do.
The road to (UI design) hell is paved with good intentions.
