[chii]

There's no real clear cut line where you can say that a model had no 'use for' a certain field.

If your point of view is that a model is meant for more than just doing the view, then yes, adding view only fields may pollute it for others (e.g., analytics).

But if your model is meant to drive the view of the app, then the story is very different. And some times you can't even tell if the model is just there to drive the view our not, since requirements change often.