Ask HN: What startup has the largest sign-up button?

The increasing proliferation of A/B-testing have the effect of inflating sign up buttons all over the web. The effect comes from the fact that A/B-testing will show that almost no matter how large you make the sign-up button, you can squeeze out a few extra per mille in conversion rate by making it even bigger.

An example of a website with a quite large sign-up button is http://www.teambox.com. Let's start a round of one-uppance: who can find the largest sign-up button around? Not counting spoofs and goofs.