EmptySpaceAds is the same start-up I was working for before I left to go back to school, so it's really exciting for me to see this development.
Now, I know ads aren't exactly exciting for most people - who likes 'em? They replace regular content and get in your way as a result. That's why EmptySpaceAds is so great - it's in the margins, so it won't replace any "real" content, and it doesn't get in your way like many pop-up ads.
For publishers, it offers similar benefits. You can increase the number ads you show on a page (and therefore your revenue), or you can replace your ad units with EmptySpaceAds. Either way, you'll see a boost in your revenue. And, best of all - you don't have to sacrifice content that brings customers to your page.