That appears to be the case with the reported leak of an iPod Touch third generation prototype with a camera module.  The radio show Covino & Rich first aired the leaked photos.  It now appears these leaked photos were for real.

Comparing them with an iFixit teardown of the newly released third generation Touch, there is ample photographic evidence that the rumor was, in fact, authentic.  The tear down reveals an identical layout, including almost all of the same circuit boards, with one crucial difference -- the release version has no camera.  Both the leaked prototype and the release version differ significantly in circuit board layout to the second generation Touch, further strengthening the argument for the images' validity.

For whatever reason, Apple appears to have late in the development process yanked the camera feature.  While the new nanos received cameras, as predicted, the Touch was left still camera-less.

Rumors continue that Apple will eventually reincorporate a camera into the device.  This certainly seems possible, as the Touch's bigger brother, the iPhone, already supports a camera module.  Until that feature lands on a release Touch, though, expect the rumors and intrigue to continue.