Ah gotcha! So you went to the publisher learn more page as opposed to our demo page. That's a good call on the call to action to sign-up being embedded in the ads themselves. Our signup URL is: http://www.emptyspaceads.com/user/new

Sidenote: It's so interesting to tail the log files and find out where users go. My friend Kalid (http://www.instacalc.com) recommended to me the free service StatCounter (http://www.statcounter.com) which is like Google Analytics... but updated live. I'm using it to watch all of you :P.