An increasing number of Internet applications take advantage of the large amount of data accessible via the Web. These applications — now often called “mashups” — make relevant information from multiple Web sites easily accessible at a single Web site. For example, back in the late 1990s, a company called Bidder’s Edge Inc. allowed users to search and compare auction data for more than 5 million items from more than 100 auction sites, such as eBay Inc. and many others, as easily as the user could search one auction site. Currently, Kayak.com lets a user compare airfares by searching numerous travel sites to find the best fares available. With such applications, a user no longer needs to visit multiple sites and manually compare data; the applications do that automatically. They extract and reuse relevant Web data, often in very innovative ways, to make the information more valuable to the user.

As Tim Berners-Lee, inventor of the Web, said in an interview published in Technology Review in 2004, “the exciting thing is serendipitous reuse of data: one person puts data up there for one thing, and another person uses it another way.” It is with that view that technologists have been developing various ways to enable easy data reuse on the Web. Despite the enthusiasm about “serendipitous reuse of data” on the Web among developers and users of such applications, the companies whose data has been reused often have tried hard to control who can use “their data” and how it is reused. eBay sued Bidder’s Edge. Online travel company Expedia Inc. sent a “cease and desist” letter to Kayak. Bidder’s Edge stopped searching eBay per a preliminary injunction court order and later ceased operation altogether. Kayak now does not incorporate Expedia and four other sites’ data in its search results; searches to those sites are performed in separate pop-up windows. Thus, it now takes a more cumbersome manual process to compare those companies’ airfares with those that Kayak automatically extracts and organizes.

Do companies like eBay