We tell the alumni explicitly that they're obliged not to disclose what they see in applications, and that if they see an application that competes with them th

We tell the alumni explicitly that they're obliged not to disclose what they see in applications, and that if they see an application that competes with them they should click on the "skip" button provided for this purpose. We can't watch over their shoulder as they do it, but we're careful about which alumni we pick as reviewers, and there has never been any problem so far.