I can't find the thread, but the solution I use is to cover the camera window with a static cling protector that has been cut out of an old screen protector with a three hole punch (it makes a bigger hole than my standard hole punch).
It covers most of the camera window and doesn't affect image quality at all. Make sure you use the clear static cling type and not the wet and dry invisible shield type. Bestskinsever includes a cover for the camera window which has an excellent fit, but it blurs the image too much, IMHO. Martin Fields, which makes an excellent static cling protector, includes a cover for the camera window which fits perfectly, but when it fell off, I didn't feel like shelling out another $16.99 just for a tiny dot to cover the camera.
So I am very happy with the hole punch solution. One left over iPhone screen protector should provide enough camera protectors for the life of the phone. The only downside I've found is that it took about four tries to get it right because the cut out camera protector was so small it was difficult to handle.
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