I am going to close this thread at this point because the question has been answered in several ways and because a poster is being argumentative.
To summarize:
Disney Dining plan may not make sense for everyone.
This is especially true for people who will not be eating or will not be eating that much. Since the Dining Plan is basically pre-paying for meals, it may be less expensive to not have the plan and just pay out of pocket.
Even when it is free, the package that includes it may not be the best value because the room will be full price, without any discounts.
Disney does require that every person on the reservation be on the Dining Plan in order to purchase the Dining Plan.
Some people with tube feedings have gotten around that requirement by adding a family member who does not eat to their room at check in. This is one of the ways Disney has suggested people in that situation could get around the requirement.
(And no one has suggested the person eat off the plates of those on the dining plan - this is the suggestion for someone who can't eat. If the person can eat, they can purchase their meals out of pocket. None of these things are cheating).
If a group/family does purchase the Dining Plan, there is no requirement regarding WHO eats the food in the group. If one member does not eat, other members of that group could use the credits.
So, finally, do the math!
Many people (my family included) have figured out that the Dining Plan does not make sense for us. We purchase Disney gift cards to use for our food budget.