You've probably heard the hubbub about the FTC changing what's allowed in testimonials, but I think something needs to be clarified. (I'm not a lawyer, this isn't legal advice, I may be totally wrong, blah, blah, blah.)
In their press release, the FTC said:
Under the revised Guides, advertisements that feature a consumer and convey his or her experience with a product or service as typical when that is not the case will be required to clearly disclose the results that consumers can generally expect. In contrast to the 1980 version of the Guides "“ which allowed advertisers to describe unusual results in a testimonial as long as they included a disclaimer such as "results not typical" "“ the revised Guides no longer contain this safe harbor.
I misunderstood this, particularly the part that says "and convey his or her experience with a product or service as typical" to mean that as long as you made it clear that their results aren't typical, you were okay -- figuring that the part about "results not typical" disclaimers referred to little disclaimers not contained inside in the testimonial.
This note is contained in the full document about the changes:
The Commission tested the communication of advertisements containing testimonials that clearly and prominently disclosed either "Results not typical" or the stronger "These testimonials are based on the experiences of a few people and you are not likely to have similar results." Neither disclosure adequately reduced the communication that the experiences depicted are generally representative. Based upon this research, the Commission believes that similar disclaimers regarding the limited applicability of an endorser's experience to what consumers may generally expect to achieve are unlikely to be effective.
They go on to say that:
an advertiser possessing reliable empirical testing demonstrating that the net impression of its advertisement with such a disclaimer is non-deceptive will avoid the risk of the initiation of such an action
In other words, if you're going to use results-based testimonials, you either need scientific proof of what results are typical (and if the testimonial isn't typical, you have to state what is typical), or you have to include a "results not typical" disclaimer and have scientific proof that consumers understand that the testimonial results aren't typical. Otherwise, have a nice time in court.
The note states that "the Commission would have the burden of proof in a law enforcement action", ie. they'd have to prove that your ad was deceptive to get a conviction, but a not-guilty verdict isn't going to pay your lawyer's fees or give you your time back.
Be aware that simply surveying your customers and asking what results they got isn't likely to be considered very scientific. Unless you take a random sample of customers and do the legwork to get responses from them (ie. bugging people who don't respond till you get a response so that you can prove that you didn't just get responses from the happy customers who wanted to share their experience), you haven't proved anything.
Personally, I think the FTC has gone too far this time. Consumers who ignore a strong, prominent disclaimer have no one to blame but themselves. Requiring sellers to prove what's typical before they're allowed to communicate of what's possible will deny opportunities to buy good products to people whose "evidence procedures" rely heavily on social proof.
One last point: I'd imagine that case studies of users of your products will be considered advertisements. If so, you may want to cover what they did, but leave out the results -- the benefits -- they got, unless you can prove their results were typical.