Someday, sometime, an employee with access to sensitive data, intellectual property, or trade secrets is going to leave your company, which makes their departure risky to the organization. Sure, you’ve “trusted” them as part of their employment, but when the time comes to change jobs, you can’t always be certain about the motive for the move. The assumption should always be they’re leaving to go to a competitor; while you normally hope for the best, you should expect and plan for the worst.