Any good programmer practices this rule, to a limited extent. Calling a function instead of rewriting the same block of code over and over again follows the DRY Principle. But Hunt and Thomas suggest taking it even further, further than I would have thought practical.
Most people take DRY to mean you shouldn't duplicate code. That's not its intention. The idea behind DRY is far grander than that.They say to do that by using code generators, automated scripts and other such tools.
DRY says that every piece of system knowledge should have one authoritative, unambiguous representation. Every piece of knowledge in the development of something should have a single representation. A system's knowledge is far broader than just its code. It refers to database schemas, test plans, the build system, even documentation.
But I think this principle can be good outside of computer contexts. I think that it could be applied to the government, at least in some situations, to make it more efficient.
What brings this to mind is changing my address. You shouldn't have to change your address twice (once for the Post Office, once for the BMV). You should be able to change your address once, in one place and have that communicated to other relevant agencies. This would make the system somewhat more complex, but also more efficient and more consistent.
I'm sure there are other bureaucracies and other real life situations this would apply to.