== Drawbacks ==
1. Abstract coupling between subject and observer: All a subject knows is that it has a list of its observers. Because subject and observer aren't tightly coupled, they can belong to different layers of abstraction in a system. 2. Support for broadcast communication: The notification that a subject sends doesn't have to specify its receiver. The subject doesn't care about how many observers are observing it, all it does is a broadcast of its current change of its state. 3. Unexpected updates: A cascade of of updates to observers and their dependent objects may occur when an observer does a change to a subject. This occurs because the observers do not know of other observers.
