Yeah, you gotta be careful about how many options you give the user. Not enough and people can't customize the app to their liking or abilities. Too many and the app becomes difficult to maintain with the number of potential settings interactions going up at an absurd rate.

This one seems on the fence in my opinion. It's unlikely to cause any weird behavior, but it's yet another settings toggle to deal with for a problem that's easily overcome by just user experience.

I'll put it this way, I have 60 apps on my phone. 57 of them do not try to keep me in the app when I try to leave with the back button. 3 of them do. 0 of them give me a toggle to change this behavior. Of the 3 that try and keep me in the app, 1 is an app which tries to keep you addicted, 1 is an app which relies on a special WiFi connection which is closed by exiting the app, and 1 I honestly can't explain why they try and keep you in there.

So if we're using that as a vote for how developers feel about this feature, it's 57 against - 3 for.

Edit: although I will say that the current behavior of the back button is pretty bad. Instead of going back up layers, it walks backward through all the screens you've been to previously.