“The decision to close the park for a for-profit event will be redeemed only if the money Live Nation paid the county to rent it out makes it a better place to visit, over the long term, for the public. Luckily, even as concertgoers were tramping across Grand Park’s lawns and through its flower beds, they were also helping demonstrate pretty clearly where its design might be tweaked and improved. They made up a huge and unwitting landscape-architecture focus group.”