I often find newsletter teasers that already include a text field that allows the user to fill in his email address. While it seems as the email was the only required field and submit would successfully subscribe the user to the newsletter submit instead loads page including the actual sign up form that asks for (additional) user data or enables the user to customize newsletter settings.
I generally like the idea of the teaser format as I'd suppose that the input field succeeds in triggering the desired interaction. However, I wonder if users feel cheated when submit will load another form.
Unfortunately – now that I was looking for real examples – I couldn't find one. I'll update my post when I found one ...