> Double inputs tend to seduce the user to copy&paste.

Maybe for us geeks, but I think your Average Joe is more likely to just re-type it.

I went through a phase of copy/pasting double inputs. That phase ended when I copy/pasted a mistake from the first input and it caused a whole lot of hassle sorting it out.

Now I just make myself type it twice. I tell myself it's for my own protection.

An option to unmask is, IMO, the best option. Please never show passwords in cleartext by default. My thoughts on the matter: http://alanhogan.com/password-masking