Interestings

Backbone.off can unbind callbacks from all instances of a class instead of just the instance you want

If you set up some bindings such as

viewClass = Backbone.View.extend({...})
view1 = new viewClass();
view2 = new viewClass();
model.bind("event", view1.myFunction, view1)
model.bind("event", view2.myFunction, view2)

and then want to unbind one of the callbacks…

model.off("event", view1.myFunction)

you will unbind both callbacks. You need to use

model.off("event", view1.myFunction, view1)

This is fundamentally because of javascript prototypes that mean view1.myFunction == view2.myFunction