[Neena]

Actually, my TV does this.
When the image gets too dark, it brightens the whole thing up a bit, so if there are really dark scenes in a movie, you don't have to sit in a completely dark room to be able to see everything.

Okay, sometimes it even annoys me (The whole screen goes darker if just a few white things appear, like a ticker on the bottom or subtitles)

But one could create a better algorithm...