Are they meant for building things like video players and custom control elements or to replace what we used can.Control for?
Take a notifications widget; you can add new dialogs to it through something like notifications.addItem("message"). Since I cannot seem to find a way to reference can.Components in this way, I would assume that this widget would need to be a can.Control. Or is it my responsibility to modify the HTML like $("notification-dialogs").append("<notification-dialog>message</notification-dialog>")?