Just to be clear, they knowingly granted him full access to all of this data (ergo, all of these PSTs). This falls completely under the auspices of "user error"

Just to be clear, they knowingly granted him full access to all of this data (ergo, all of these PSTs). This falls completely under the auspices of "user error", and PST is no more to blame than if they granted administrator access to every user. This is a boring argument that only takes place because people can throw down the tired, unsupported "damn that Microsoft!" card. Sorry, but the reality is more correctly "Damn the intelligence community and inept safeguards and data controls."