The idea is not really that sources must be public, it is rather a response to the very common retractions of the form "turns out our sources lied to us and the

The idea is not really that sources must be public, it is rather a response to the very common retractions of the form "turns out our sources lied to us and the whole story was based on one source, also in the future you won't have a way to know whether we will use this source again."