What's difficult for me to understand about this is the liability. Clearly, if a 60mph gust of wind comes up, that's an "act of God" and I doubt very much whether there is any real liability of the riggers or the organizers for something like that. Demonstrating clear incompetence or culpability for this accident is going to be difficult.
Having said that, these are actually fans of Sugarland that are suing; loyalty means nothing, I guess. And, so much for all of that praying Sugarland likes to do. No amount of piety will get you past a legal nightmare nowadays.