This policy indicates problems on more than one front. First, it could mean a poor management issue. No employee, save top executives, should be so vital to the company that he or she can't be out of touch for five business days without disaster striking or the business grinding to a halt.
If your staffing situation is so lean that you don't have at least one capable backup for each person who performs important daily work, you have a big problem. This includes sales representatives. It doesn't matter how close the relationship between sales rep and client -- if the rep hasn't prepared the client and his or her backup for anticipated problems, then the rep hasn't been properly trained or managed.
This incommunicado policy should be maintained even in an "emergency." For example, I know an employee who was expected to take part in a meeting via phone while on vacation, because one member of the team had turned in his resignation and the supervisor wanted to realign the workload. The employee gave two weeks notice, so there was no reason this meeting couldn't have waited until the vacationing employee returned.
Next, there's the human resource aspect. With today's leaner companies, employees are shouldering bigger burdens. Add to this the usual stressors of work and you have employees -- including sales reps -- who need and deserve a week stress-free. And doesn't the employee's family deserve his or her undivided attention?
The employee isn't the only benefactor of a hands-off vacation policy. Employees allowed to enjoy a week free of work stress usually return to work relaxed, recharged and ready to tackle any problem.
So if your company's policy is to require employees to call in while on vacation, rethink it. Giving them an uninterrupted week off is a win-win situation for everyone.