I was skeptical myself when I first heard of it. Kept asking myself how can this happen.
When I bought the Nikon D90, it had dead pixels on it's CCD believe it or not. They showed up in really dark pictures all the time.
The iSight is not exempted from this because it uses the same tech.
Test yours by covering it with the black cloth that came with your mac and take a picture. Enlarge it and check to see if you have any.
