Microsoft let streamers know ahead of its big showcase on Sunday that co-streaming is encouraged. It obtained all the re-transmission rights to the music featured in its trailers for up to twelve months, giving streamers ample time to hype the games with their audiences before the VODs need to be removed. Nintendo took the opposite approach, discouraging Twitch streamers from co-streaming the event entirely.
Source: Nintendo Warns Twitch Streamers – ‘Don’t Co-Stream E3 Showcase’