Today it was a difficult task to find out some scientific video that I watched last monday (wanted to refer to it once again because I got some idea! 
) and I was not able to find it out. Had to go to web browser's history (thank god, i saw that on that machine only! othewise it would not have been possible!)
So, here is the feature,
YouTube should remember history of all the videos I watched anytime and they can also give history search feature!
I hope this idea click in some of the engineer from YouTube Team and they develop it as soon as possible!!
Stay tuned.. 