Have separation between levels of security and have fewer & fewer admins working on them as you go up the chain. Use the old established and trusted guys at the top. Don't have thousands of people (particularly contractors) crawling all over the most sensitive data. Seems obvious really. Look at the amount of data *Private* Bradley Manning got his hands on. It's like NSA & Govt just leave the barn doors open and hope the fear of prosecution will prevent the bad thing from happening.