Johnny.Decimal – A system to organise projects

I see a few potential problems with this.

First, people in practice use folders for a few different things and it causes workflow problems when they can't use folders in flexible ways. (citation: "Don’t Take My Folders Away! Organizing Personal Information to Get Things Done", William Jones et al)

Second, despite the claim that "There's only one place anything can ever be," a hierarchical system allows only one of many possible (and conflicting) ways of organizing things. It's commonplace in just about any taxonomy to encounter items about which users have conflicting opinions about where to file, and items that could legitimately belong to multiple categories.

Third, to the extent that it accomplishes any of the stated goals, it does so to no greater extent than a standard, name-based folder hierarchy. The point here seems to be that by using numbers, companies can be freed from even the burden of having sensible and consistent naming... or that for example people can be made to say "12.04" instead of "the Payroll project for onboarding or something. I see this as unrealistic. Should manager correct those who use English, and instead have them use the inherently meaningless numbers?

Fourth, no one in practice will want to use a system called "Johnny.Decimal" Regular people have to be able to say something with a straight face, and not feel a little bit silly.

Most companies I've worked at who still used a share drive had a system like this.

Very simple and effective.