Should this be `subscribeOn` instead of `observeOn`?

For example, in the other pull request https://github.com/Netflix/RxJava/pull/415/files#diff-5ec494b927739f6fefe3a4d351a9dd05R566 it uses `subscribeOn`.

I believe we want `subscribeOn` so the actual subscription and callbacks occur on that scheduler instead of observeOn which schedules each notification on a separate scheduler but doesn't change where the work is done.

In this case it has little practical effect as all it does is throw, but I'd like consistency, and `subscribeOn` is the more efficient and accurate approach I think?