I am no expert so I am speaking purely as a consumer. On a new camera, I expect all the pixels to be working. If they aren't or even if they don't guarantee it, I would be upset, and if I knew beforehand I would likely not buy the camera.
This raises a question about buying 2nd hand digital cameras, which will become more and more of an issue. It's one more thing to check for. The question arises about how or whether bad pixels are "fixed". Do they exchange the sensor? Do they mask the bad pixels using interpolation algorithms the way bad blocks on a hard disk are mapped out of usage? How DOES one check for this?
Theoretically, I could own a few bad pixels and never know it. One could then say that if I didn't notice then it's not a problem, something with which I would not agree, BTW. Whether I notice or not, I am not getting what I thought I was paying for.
If bad pixels are "masked" out in this manner, it would seem to me that the industry and equipment reviewers should be making this clear to the user community. If I knew that camera A fixes this problem by "masking" a pixel out of usage, while camera B does NOT, it affects which one I may choose to buy. But I can't say that I have seen this issue mentioned very much. Whether it's because it's a non-issue or not, I don't know. I hope that electonics experts can shed some light on this.