This is a good way to lose a sale. Like the person you are responding to said, I have done user funnel work and every step between the desire to purchase and completing the purchase is dropping users out the funnel. This is the idea behind retailers like Amazon introducing one click purchase. If someone has the impulse to buy you want to get as out of their way as possible.
I wonder... what if you artificially padded the signup process with feel-good stuff?
- screen: Did you know, <picture of Scarlett Johansson> Scarlett also uses this service?
- screen: Since you are signing up, we are adding a Free 10% off voucher for <stuff!>
- screen: Our customer Service Representative (attactive person) is always standing by!
etc...
- screen <n>: click [Yes] to sign up!