I can safely say this is the first time I've heard of Mixer.
Did you hear about Beam? (think they renamed it to mixer a few years ago).
Anyways MS version of a streaming site for gameing.
Necro-bump this 2020: http://gamrconnect.vgchartz.com/thread.php?id=229249
Bumb in 2021: http://gamrconnect.vgchartz.com/post.php?id=9047071