Would it be a complete disaster if hundreds or thousands of Twitch.tv users controlled a single champion in a League of Legends, similarly to 'Twitch plays Pokémon'? YouTuber shocknickfilms' parody shows us that yes, it would be pretty catastrophic.
And how do you control the mouse? You can always type "LEFT CLICK" or "RIGHT CLICK" in the chat. Someone better do this with StarCraft II, straight away!
If Twitch.tv Played League of Legends- (twitch Plays Pokemon Parody) [shocknickfilms, YouTube]