These kinds of form improvements should be done for trying out services that the user already is familiar with, like buying a car, getting a insurance quote, and where there are multiple choices of service providers, right?
Because, on a sign up form for a new web service, I really don't want users to be tricked into signing up. I only want those users who understand what my service offers (through the intro blurb, videos etc) to sign up and if you have decided to try based on the merit, why would a form design matter? If I lost a sign up due to a form design, my service is probably weak, no?
Even something as simple as asking for an email address in addition to username/password will lose you a percentage of signups. (As a real-world example, we tried removing all the fields from the signup page on Twiddla and saw a 1000% increase in users trying us out).
This form design seems to be a way of convincing people that they're not looking at a form, and therefore tricking them into filling it in to go do the thing they wanted to do in the first place.