Right now, a user will not get notified when a new blog post has been published in a subscribed space. This is only possible if the user watches the space blog using Confluence core functionality.
Getting both (subscribed news in cover stories/news stream AND notifications) is therefore quite cumbersome. Many users are quite frustrated.
So I suggest that a user can not only subscribe to spaces, but also decide on a space-by-space basis wether he wants to be notified if new posts are published.