you should be back in preschool as your understanding of what your talkin about is minimal...
1 - 99% of LED screens are not back lit

they are edge lit...backlit is still a very EARLY technology and only features on VERY high end panels
2 - plasma burn in isnt "black dots", its image retention/ghosting...meaning you will get a faint image (game minimaps, dvd menus, tv inputs, channel logos etc) showing in particular shades
3 - LCD/LED screens however get "black dots"...they are known as dead pixels...