I read somewhere that these faint lines are due to the gamma values being set incorrectly on displays. So LG have screwed it up in the factory.
All displays don't have this as some people are saying. My old HTC Hero didn't have it, my ipad 3 doesn't have it, iPhone 4, iPhone 5, iPhone 4S, SGS2. All perfect displays. I don't think there's much you can do apart from messing about with colour control but you have to root to do that and it probably won't really make a difference.
My problem is three or four faint wide lines visible on grey or white backgrounds, gonna call Google and ask them what it is.