Auto orders would likely be reserved for essentials - milk and eggs. If they have a built in egg holder, the fridge knows how many eggs you have. When you have three or less, it orders a dozen more. Milk has a set expiration date. Add a scale in the door where the milk gets set, and the fridge could know (based on info given when the milk is ordered and the weight) when the milk is low and if the milk has gone bad.

Most likely the auto-order function wouldn't be used as much as manual order---you create your grocery list on an app or online (I already create my list on the Smith's app every week), bluetooth it over to the fridge, which combines that list with your list of auto orders, and voila! things show up on the doorstep the next day.