A free Internet site that maintains a database of product reviews that has advertisement banners is

Question

Quizplus · Accepted Answer

The site is privately-provided as it is not provided by the government. It is a public good because it can be accessed by anyone with an internet connection and one person's use of the site does not diminish its usefulness to others. However, it is also excludable in the sense that the site's owners can choose to restrict access to those who do not meet certain criteria (e.g. login required). Finally, the site is selling advertising space, which is a by-product of its main function, making it a privately-provided public good selling its by-product to advertisers.

A Free Internet Site That Maintains a Database of Product