Some rules to remember when writing Ember.js code

• Display logic only goes in the view layer
• Never modify the DOM in View API
• App logic only goes in the controller layer
• Limit custom code in the controller
• Domain logic only goes in the model layer
• Server calls belong to the model layer
• Only cross layers going up (V -> C -> M)
• Never observe across layers

From Sproutcore Training: Part 2 - Core Concepts