So why should the government develop its own URL shortener, when there are others out there?
The first reason -- and this is where I see potential value to others -- is about the government brand. When government links are shortened to bit.ly or tiny.cc, nobody knows where the site goes until they click on it. With go.usa.gov, even though the URL is shortened, it's obvious that the link goes to a United States government Website. Other companies and organizations could do the same thing.
Stability was another reason the GSA decided to do this internally. Earlier this year, URL shortener Cligs was hacked, and Tr.im temporarily shut down, taking all its links with it. The government, with its visibility and archiving requirement, can't have that, and organizations that use URL shorteners shouldn't stand for it either.
By developing an internal URL shortner, the GSA also got the ability to manage all its shortened URLs centrally, managing its own user accounts and gathering metrics on what is popular and what isn't rather than the guessing game used when links are spread out over a number of URL shorteners.
Lastly, the effort hasn't really wasted any money. To develop the service, GSA borrowed a developer from the Department of Veterans Affairs, who developed a new open source module in Drupal to shorten URLs, and contributed that code back to the Drupal community. The service runs in GSA's the Terremark-hosted USA.gov cloud, so GSA didn't have to stand up new servers or bother with a new hostname.