As we were discussing on the IRC, I think it would be nice if you could somehow declare a set of default attributes for a model that would get automatically set to their associated values when a model is initialized.

I think the implementation could be something along the lines of what you suggested:

Backbone.Model.extend({ 
    defaultAttributes: {
        key: 'value',
        anotherKey: 'Its value'
    }
});

or even simpler:

Backbone.Model.extend({
    defaults: {
        key: 'value',
        anotherKey: 'Its value'
    }
});