A study in New York City found people bought 50 fewer calories, on average, when this data was made clearly available. A Stanford study, released this year, showed a 6% reduction in calories purchased when the data was in plain sight.
But some of the data is surprising, as Michael Pollan noted to The Washington Post recently. If you know that salad, with crispy chicken and dressing, has more calories than the Big Mac, I'll have some health righteousness with my burger, thanks.
And many restaurants have gotten good at hiding fat in free side dishes, as I noted at SmartPlanet. When the sides are added, restaurant calorie counts can be 18% higher than advertised.
Something else to consider. This requirement is waived for non-chain restaurants, or chains with fewer than 20 stores. So places like my locavore pub, Leons Full Service, are exempt. (Try the bacon in a glass with peanut butter.)
Same that fine local soul food chain, This is It!. If you really hate this regulation make these two guys your big brothers, at least until they get 14 more locations.
For the rest, this little experiment in social engineering is going mass market.