I decided I don't want anything from the user at signup. Well, except
an email, a password and possibly a captcha to skip the email
I want my login form to do signup as well.
When the user presses submit, if the email is not in the db, I tell
him to enter the captcha and, after a second submit, i present him
with his dashboard.
There is of course a use case for users that forgot their account data.
What do you think about this when comparing with the classic login
form + additional "new account" button? And ... is it viable for
signups that require additional data (to be presented in the 2nd step,
with the captcha).