A credible testimonial can be a powerful influencer, whether for an advertiser or for our own stations. The operative word there is "credible." If it sounds scripted or forced, even though it's true, it may not be believable, as you can hear in this actual comparison I wrote about some years back.
Are you using testimonials from your own advertisers, either on the air or on your website? How many do you have? How often do you update or add to them? And what kind of feedback have you had from them?