I was wondering why I kept getting read errors when verifying writes to a particular DVD+RW. Now I know why. There is a sort of black dashed arc, concentric with the DVD. It is below the surface and it is not a scratch. Here is a photo:
The defective area is in the middle. Near it you can also see two pieces of dust. Note how dust leads to double images because you see both the dust and its reflection on the recording surface. The defective area doesn't have double images because the dark bits are at the recording surface itself. The black circle at the bottom is a shadow from the camera lens. At the bottom right you can see the centre of the DVD. Note how the curvature is parallel to the curvature of the defective area. The entire image also shows a reflection of the lamp that provided illumination.
Edit: I guess the Sony lifetime limited warranty is pretty much worthless in a case like this. The only contact number isn't toll free and the warranty instructions say I should mail in the disc. Buying a replacement is probably cheaper and easier.