It appears that Nintendo is going on a spree, removing Super Mario speed run videos from YouTube.
While speed run videos are typically protected as fair use, but Nintendo and Google has agreed that tool assisted speed runs do not enjoy the same protection. In tool assisted speed runs, Mario's actions are controlled by a program rather than a human player. This typically requires the use of emulators which Nintendo believes to be illegal.
Technically, emulators fall in a legal grey zone. They are legal to use only as a way to play games you already own and extracted their ROMs by yourself. Given the fact that most of the games in question haven't been in circulation for more than 20 years, it is hard to believe that those criteria were met by any of the speedrunners.
Alex Losego, a famous speedrunner, believes that Nintendo's actions are fueled by the recent release of Super Mario Maker. "I think it is stupid of them to go after TAS videos, but then again they have every right to do so," he said. "And yes, I think this has everything to do with ‘Super Mario Maker’ being released recently. Seeing how the game is a great hit, my guess is that they don’t want people to stumble upon videos that cross the fuzzy legal line (TASes, hacks, etc.) when they search for the new game. I wouldn’t be surprised if this ‘attack’ is only temporary — take down videos in between the game’s release and this holiday season (the time where most copies of Super Mario Maker will be sold)."