Okay, I'm going to use an example from the presidential campaign to demonstrate the difference between great third party endorsement and standard testimonial.
Put aside your party preferences for a moment to understand how PR has the power to persuade. Let's look at Senator John McCain and Senator Barack Obama as products.
The Market Leader
McCain would be the market leader. The market leader is well established in the marketplace, has been the reliable technology used for many years, and is the accepted method of practice in the industry.
The New Product
Obama would be considered the new product competing to take over the market. Because the new product doesn't have the same credentials and longevity in the industry, the new technology must find a way to persuade the masses that this product is better that the standard.
Traditional Marketing vs Strategic PR
The market leader has endorsements from 200 generals and five ex secretaries of state. The market leader touts its endorsements by using the names of industry leaders in a publicity campaign, but fails to get specifics from those leaders. This is more traditional marketing testimonial that says product X is best that doesn't attract much media attention.
The new product gained public endorsement from an industry leader that has been dedicated to the standard technology (Colin Powell), and this industry leader gave specific examples of why the new technology was better than the old technology. This is powerful endorsement that gains a great deal of media attention.
Media coverage is gained when someone else paints a picture of how a product or service offers a solution, not when one touts how great it is.