The FAA wants to be sure you know that you are NOT allowed to operate your UAV in a "careless or reckless" manor. It goes without saying that if you are a professional drone aviator, the safety of the people and property around you should be your top priority.
Being careless and reckless isn't limited to obvious and egregious actions - such as playing chicken with cars on the interstate or flying 40 MPH while six inches above a crowd of strangers. The FAA has said that something as simple as failing to take adverse weather into consideration when conducting a higher risk flight operation, such as flying over people, could be considered "reckless." So always be sure to lean on the side of caution when making decisions about flight operations.