Temporarily.
They come back after usage, at least here.
It's a heat related issue, it appears.
From the same page:
Picked up my iphone today, took me a good hour before i noticed i had a yellow blotch in the lower left of the screen, about where the left of the unlock slider is. Read this, pumped up my brightness to max, and continued to use it, it appears to fading down already, admittedly mine was fairly small in the first place in comparison to some i have seen, but this solution at least appears to be working for now.
Hope this helps.
While heat-related (it shows up after some use), that does not mean what I posted is false. It could need time to evaporate, and simply show up during heat while it has not completely evaporated. Furthermore, check engadget. They featured the exact same post.