I don't know about Gox, but I was setting up a Paxum account and they have stricter AML/KYC rules. They said if you black anything out it will fail verification. They (Paxum, again) also go total nazi on the requirements and say it has to be in full color, can't touch the edges of the document, has to be centered, has to be ultra high resolution, etc, etc.
Well that would just be completely unacceptable. There is absolutely no way I would scan a document and send it to someone with my credit card number on it. My ISP sends bills through email and they are also my phone company. I do not own a cell phone so I do not have a bill for that. Therefor I would not be able to "verify" my identity without compromising my identity.