klyster: I think it's light from the screen travelling down to the edge and the edge isn't masked properly along the edges.
It isn't light bleed in the traditional sense, it's more refraction....imo of course.
I think it's just because the screen/glass is curved and the light that comes from the edges of the screen is 'directed' away from your face, appearing dim. And when you view the phone from an angle you seen the edges 'head-on' and see them at their proper brightness.