"Bigger, Stronger, Faster," an excellent documentary about the use of anabolic steroids, features a segment in which a professional photographer demonstrates how "before" and "after" photos can be faked by companies that sell fitness products and supplements:
The Las Vegas Weekly also recently wrote about how to fake before-and-after photos.
I'm not suggesting that Beachbody engages in Photoshop trickery. I'm pretty confident that the photos of "real people" featured in P90X ads are real (though, as Begin to Dig has pointed out, the company may use more dramatic lighting and slimming poses to further enhance P90X grads' legitimately ripped physiques in some of the "after" shots).
But the next time someone trots out "before" and "after" photos to try to get you to buy something, be skeptical. And if you catch the fakery, kick 'em in the balls for me.