When you say:
You would then make sure to update your add to cart server behavior so that this column has a value by default. You can enter a value or get it from an input in your add to cart form.
Does this mean I have to go to each and every single add to cart button and put in a default value? If so, what would that value be? These two radio buttons will be intended to ask the shopper if the line item is for "personal" or "business" use, so there is nothing to pull from a database...???