I was having a look at BarackObama.com yesterday and noticed that they are doing some multivariate testing on the namesqueeze page to increase the number of signups. The variables they are testing are the background image on the page and the message just above the signup box.
There appears to be two different (but very similar) messages:
Welcome to barackobama.com! Sign up now to learn more about Barack Obama's position on the issues
Sign up now to learn more about Barack Obama's position on the issues
The other (more significant) variable is the background image. The variations seems to be:
I was only able to see the combinations by changing the filename of the image (1 through to 4) so it seems that the one that is showing at the moment is the best performer.