I trip out every time I look at the source of it and Underscore. There's nothing there, it's all so simple, it's like the bare minimum amount of code that can be there to do the things it does.

Backbone aka. Memory leaks as a service

Which is the reason Marionette exists in the first place (well that and boilerplate code).

If you create a bunch of stuff then don't dereference/unlink/whatever you want to call it in JS-land it you're going to have a bunch of references to stuff laying around. I don't fault Backbone for that.