When famous actors or sporting superstars appear in television or print advertisements extolling the delights of particular products, even the least alert consumers will probably conclude that money has changed hands. But the advertising world now extends far beyond such straightforward celebrity endorsements into areas where the links between the product and the person promoting it can be far less clear-cut. In this landscape, the US Federal Trade Commission is right to insist on more transparency.

The rules published by the FTC this week are the first revision to the guidelines on testimonials for almost 30 years. As well as spelling out the liabilities of all those involved in making claims that turn out to be unsubstantiated or untrue, they require people endorsing a product to be explicit about any payments or freebies they have received. This applies both to the celebrity chatting on a talk show or tweeting on Twitter, and the blogger writing a review.