I used to be part of a phone support group for a large retail-photography company. I swear, some of those people had the same mental age as the children they were shooting.
Now bear in mind, this is a *professional* photography studio. Both the $2000 camera and the $5000+ multiple-source lighting system have been painstakingly calibrated for exposure (brightness) and color balance.
The lighting system has a loud, deliberately obnoxious alarm beeper that goes off whenever there's a problem with the flash, and you'd have to be blind not to see the flash going off.
Despite all these precautions, I still got the following call at least twice a day:
Caller: All my pictures came out totally black, can you fix it?
Me: I'll see what I can do, did the flash go off when you took a picture?
Caller: I think so, the beeper went off every time I pushed the silver button.
Me: I'm sorry ma'am, that's the alarm. I can help you fix the lighting system, but you'll have to reshoot.
Caller: But I can't, the family's already gone home while the mom picks out the pictures.
Caller: You can fix it though, it's a digital camera, right?
Me, thinking [**Sure, let me just hop in my time-machine so I can magically recover all the light photons that never made it to your camera...**]
Despite what CSI makes you think, no amount of retouching can fix a completely unexposed picture, no matter how expensive the camera is. Underexposed, yes. Unexposed, no.