The idea with emptyspaceads is that your site's empty space isn't providing you any value beyond simple aesthetics. Firstly, the ads only appear when when your user's mouse is in the empty space of your site, and they only appear within your site's empty space. So for some users, they'll never see the ads.
You can create your own TextAds, ImageAds, or even HTMLAds. These allow you to drive users to content on your website or blog that you monetize well (a CafePress store for example), or behavior you'd like to encourage (like more RSS subscribers). (See our
blog for an example how we use emptyspaceads to get more RSS subscribers to our blog by embedding the feedburner chicklet). Or our Sample TextAd, ImageAd, or NetworkAd... our check out our
demo.
I think the potential interest for e-commerce sites is using our product to offer a 5% or $5 off coupon that appears in your wesbite's empty space. I think it's like putting a coupon outside a department store... not everyone who sees it will want to pick it up... but it will give an excuse for more frugal people to buy your products & services.
-David