1) Big data technologies can provide advantages to companies like cost savings and performance improvements, but also pose security risks as data breaches continue to rise. 2) Five common mistakes that leave companies vulnerable are: running databases in trusted environments, loose access control, relying on static protection schemes, inadequate detection of sensitive data, and lack of entitlement monitoring and auditing. 3) To properly secure big data, companies need to know where sensitive data is located, limit access, and implement dynamic protection and monitoring strategies.