You would need to inquire with eBay about what types of products can be listed how. Our eBay integration simply allows our system to be notified when you have an eBay sale for an item matching a product you've configured in E-junkie, so we can process the sale like we would normally for that product. See our eBay integration procedure here:
http://www.e-junkie.com/ej/help.ebay.htm
For instance, your product might have a download component -- like a manual that goes with a physical product, or a downloadable version of files or music you're selling on a CD/DVD -- or you might want all your eBay and other online sales to be logged together in E-junkie, or you might want every buyer to receive your usual E-junkie thank-you email message.