The ads on the site are actually a first hint towards future functionality; We are currently developing a system that automatically cross-references information on your lists with other resources that may be of use to you. So it's not about the cash (which doesn't make us rich, I can tell you ;) but about helping you discovering interesting resources while using Listdings. And hey, even the ads are interesting sometimes...
Once the planned auto-referencing system is in place you will be able to configure which kind of links show up on your lists.