L.C.E.C. on 22 June 2009
It makes the surrounding area to the video darker, like in a real room.
More importantly, It hides all comments, most importantly, SPOILERS.
Try it out, as this was the video I noticed it on and which was the only one I could find both features on :
http://www.youtube.com/watch?v=xpXK8mDTiNg
I think it's cool and VERY useful...
