i’m happy to type my password twice when i fill in a web registration form. it’s starred out and i can’t proof that it’s right. in fact i often don’t recognise my passwords when they’re presented in plain text, they don’t mean anything to me that way.
but why oh why do i increasingly need to type my email address twice? look, i can see it’s right the first time!
my experience with being “postmaster@” and getting tons of bounced mail from attempted registrees is that you can ask users to type their email address as many times as you like, some of them just plain don’t know what an email address is. they put all dots and no ats. they put spaces in them. they type urls. they just type their names or handles. syntax checking might help. i’m not convinced that typing twice helps anyone, it just takes 17 keypresses off my life (plus a tab.)