Facebook advertising: Who likes my virtual bagels?
Much of the value of social networking giant Facebook is based on its actual, and potential, revenue from advertising.
The BBC technology correspondent Rory Cellan-Jones has conducted an experiment to test the value of "likes" prized by so many big brands, and the usefulness of Facebook's advertising.
He explains how he conducted his experiment, by setting up a fictional "virtual bagel" company.
Asked about the issue, Facebook said it had "not seen evidence of a significant problem".
And more about Facebook's reaction here.