If the parent is the only place where there's a reference to the child view, then yes. However like the article says, you often have things like event listeners that, if the child view doesn't clean up, will prevent the child view from getting collected. (And often, the listeners still do stuff causing buggy behavior.)
Yes, but if they are bound to the child's element and that is removed shouldn't that be sufficient unless the view is binding to other elements or window events?
The problem is, you have a bunch of subviews which are registering events on some collection models... when you rerender your parent view your subviews get recreated but your previously created subviews stay in memory because the backbone events system still stores references to the old views which aren't really needed anymore. The only solution is to explicitly remove the events when subviews a destroyed (or better use a solution like in the submitted article) or use a library like https://github.com/marionettejs/backbone.eventbinder
This is fixed by ensuring there's an off()/unbind() for every on()/bind(). I do this by following a pattern like the one in this article: http://lostechies.com/derickbailey/2011/09/15/zombies-run-ma...