To be honest, I didn't put much more thought in to it. I saw the studies about people eating more from large containers floating around, but I dismissed on the basis that (like with the vending machine theory) they were skipping a crucial step. Even if this ban got people to drink less soda, that doesn't actually prove it would reduce obesity. You have to prove all the steps in the series to prove the conclusion.
A few days ago, the authors of the "bigger containers cause people to eat more" study published their own rebuttal to the ban. In an excellent example of the clash of politics and research, they claim that to apply their work on portion sizes in this manor is a misreading of the body of their work. They highlight that the larger containers study was done by assigning portion sizes at random, to subjects who had no expectations as to what they would be getting. In their words, the ban is a problem because (highlight mine):
Banning larger sizes is a visible and controversial idea. If it fails, no one will trust that the next big -- and perhaps better -- idea will work, because "Look what happened in New York City." It poisons the water for ideas that may have more potential.
Second, 150 years of research in food economics tells us that people get what they want. Someone who buys a 32-ounce soft drink wants a 32-ounce soft drink. He or she will go to a place that offers fountain refills, or buy two. If the people who want them don't have much money, they might cut back on fruits or vegetables or a bit of their family meal budget.In essence, by removing the random element and forcibly replacing what people want with something the don't, you frequently will have the worst possible effect: rebellion.
Mindless eating can be a problem, but rebellious eating is even worse.
When the researchers you're trying to use to back yourself up start protesting your policies, you know you got it all wrong.