[icebraining]

Validity? It's a string like any other. It's not mkdir's job to second-guess what I tell it to do.

And I don't see how it violated such principle. You tell it to create a file with spaces - you even emphasized them with quotes -, and you're surprise it did so?

[harrytuttle]

It is merely an illustration. The reality is stuff like that occasionally does happen when you use variables and parse results from other commands.