As I wrote this earlier month, doctors often know when a patient has been the victim of a medical error – sometimes before the patient does. But too often they don't say anything about the mistakes, according to a recent report in The New England Journal of Medicine. Feedback to the post was so thoughtful that ProPublica decided to host a Google + hangout about the topic. We invited four experts to join us – two doctors and two patient advocates. Here are five takeaways from the conversation.