I was hoping we could wrap all ajax calls in models, however that's assuming a user instance already exists.  At this point a user isn't logged in, however at this point we always inject the User mock into every controller instance.  In the future it may be we have a user instance but just no properties defined as no logged in User exists.

For the time being I'd still like to see this in the [User model](https://github.com/TryGhost/Ghost/blob/ember/core/client/models/user.js) and expose a `forgottenPassword(data)` function on the class.  Seems like proper encapsulation to me.

This also goes for the validator you use above, that should really be in the User model as well.