This is obvious in the case of email or personal Web pages, but in other cases it is not so obvious.
Consider three successful Internet businesses: Ebay, Amazon, Yahoo and Google. Each owes its success to user-supplied content.
1. You can access your bookmarks from any computer with a Web browser and an Internet connection. 2. More important, the entire bookmark database may be analyzed and shared.
When you add a bookmark to the database, you can also supply a comment that further describes it and tags you use to classify it.
This metadata (data describing data) is available to the del.icio.us search engine. It is able to tell you who has bookmarked a page and what comments and tags they used.
In each of these examples, the user receives a benefit which induces them to use the service, and the community gets the benefit of the collected database.
With Del.icio.us, Ebay, Google and Amazon transaction data, the user merely uses the service. In the case of Amazon reviews, the user must make the effort to add data for the sake of the community. In the case of Amazon, the information is explicitly added, whereas it is implicitly added by using the other services.
In other cases users may be required to contribute content to a community database. For example, in a corporation, different people are responsible for keeping portions of the Web site current.