How accurate does it need to be?

Time and time again I get asked "How accurate it the map?" Well it depends on what you mean by accurate. Like any industry there are tolerances, acceptable or not there are tolerances. Take a set of house plans for instance. The interior walls may be dimension as being 4 -5/8" thick(3- 5/8" stud and two sheets of 1/2" drywall). Now if we got the old micrometer and check an as-built wall we come up with something different. In architecture we allow a 1/16" or even as much as 1/4" tolerances and call it good. So what should we use as a tolerance range in maps?