Developers who choose to bundle the Sun JSF Reference Implementation with their WAR will get strange errors like ERROR [javax.faces.webapp.UIComponentTag] Faces context not found. getResponseWriter will fail. Check if the FacesServlet has been initialized at all in your web.xml.
This is because of collisions between classes provided in both implementations which are required to have the same javax.faces package name. We should be able to detect if the RI is present and tell the user to either remove the RI, remove MyFaces, or scope the deployment.