Mandatory vacations - Much like job rotation, mandatory vacations provide the opportunity to detect fraud. When people are on vacation, their access to the site should be suspended. This prevents working from home (possibly covering their tracks) and provides them with the much needed vacation they have earned.
Under US Banking rules, employees of retail banks (those with savings or checking accounts) must take two consecutive weeks of vacation. Until recently, they were forbidden from contact with work-related matters. That rule has been relaxed to allow for read-only content so they can keep up on emails and such, but they are still not allowed to participate.