The problem they will face is not that gamers are loyal so much as for many people "live video game broadcast" is Twitch, so people are unlikely to notice live streams if they're elsewhere. This is solvable though - most streamers upload their VODs to YouTube anyway so they can easily notify users when a streamer is live.
2) Amazon could surely afford to compete with Google on sub share % if need be. Furthermore, it's not just a matter of offering a higher sub share. It's (sub share) * (# of subs). Twitch has a very good head start on the latter.
twitch infrastructure is notoriously bad for anyone that is not american.
Fro a Dota perspective competition like MLG, Hitbox, DailyMotion and Azubu have gone down the path of getting exclusive events and a lot of the audience generally follows.
There is also the massive Chinese market which is generally siloed from the rest of the world.
One thing other sites struggle with is getting the same Chat experience that a lot of people like from Twitch for big events.
Not sure Gamers like that whole censorship thing. Ask yourself why GTA is the best selling game on Steam, while constantly being shit on by both the Social Justice Left and the Christian Right.