This affects all cameras.
There are 2 routes for light to get to the sensor, the obvious route is through the lens to the sensor, the other route is through the eye piece. You normally have your eye and head against the eye piece blocking the light, but when you use live view, light is free to enter the eye piece.
I've never had an issue with this and most won't
Times it can cause an issue is when you are using an ND filter and the light entering through the eye piece will be much stronger than entering through the lens.
It can also come up on long exposures and also I believe you can get reflections off filters in front of the lens when the eye piece is uncovered.
This is all in theory and from what I have read on here, I've not seen any signs of this on my D3100