Opt out of automatically viewing a new stream
There are times when I don't want to load in to a new stream after the one I was watching is over.
Some examples are when I am alt-tabbed and playing a game.
For me personally, while playing a game I will always experience a spike in bandwidth usage while the new hosted stream loads in.
Not all streams will use the same bitrate either, which is a concern, however I've not had issues with that problem so far.
Another example is when I am away from the computer, viewing twitch as it were actual TV.
Then inevitably having my ears blasted off by a hosted streamer with much higher audio settings.
I overall enjoy hosting as a feature, but there are times when it's not appropriate to have.
At least not now while stream-to-stream settings across twitch are not standardized in any way.

-
Ken commented
Agree completely.
Hosting has done some good things for the twitch community; but viewers should have the option to opt out of it.
If opted out, instead of auto-playing the hosted video, put a thumbnail of it (like you were looking at it on the browse page) over the hoster's offline image.You can be like: Abc thinks you might like Xyz. [Watch here] (start playing the viewer as if it was hosted) [Go there] (jump to that streamer's page, like that button that appears at the top of a hoster's chat)