Japan's postal service, which is owned by the Ministry of Finance but run more like a private company, shows how far a privatized postal service -- or a partly privatized one -- could go. Japan Post is among the country's largest bank and insurance conglomerates. What exactly a private U.S. Postal Service could do is open to debate. We think of it as an essential government service, but its services are limited by that view that they're essential. And FedEx and UPS might wind up better companies if the Postal Service was privatized. How much better might those two companies be if they were facing a more direct threat from a private Postal Service unbound by old-fashioned notions of what it had to do, one that could do anything its managers thought it could make money doing? At the time of publication, the author owned no shares in companies mentioned here.Follow @DanaBlankenhorThis article is commentary by an independent contributor, separate from TheStreet's regular news coverage.