I've been asked many times whether testimonials are even worth the hassle. The answer to that depends upon your prospect but the truth of the matter is that our general population is made up of about 40% who make internal-only decisions, 40% who make decisions based on what others have done, and about 20% who make decisions based on a combination of the two. (As a general rule, the younger we are the more importance we place on others' experiences.. and the older we get the less importance we place on the experiences of others).
So since about 60% of the general population base their decisions in some part based on what others do or have done, I think it's wise to use testimonials...on your website, on your collateral, print ads, etc. According to Dan Kennedy, the direct mail guru, adding a testimonial(s) to your copy increases response.
"Social proof" is the term used for the tool that influences those who use external sources to make decisions. Social proof comes in the form of testimonials, case studies, a mention in the newspaper or a printed article, etc. The bottom line is that a large percentage of your target market is externally influenced so I believe that testimonials are definitely worth it. What do you think?