From their site: Dapper aims to make it easy and possible for anyone to extract and reuse content from any website. The Dapp search web service provides a programmatic interface for searching Dapps and their properties. This is the same web service used by the Dapper website on the find a Dapp page.
One of the many frustrations that mashup developers (and web developers in general) run into is trying to use contextual ads for sites with lots of dynamic content. By their very nature, mashups typically tap into data that constantly changes, making it difficult to use contextual ads that stay up-to-date with content.