Hallway usability testing, TDD and pair programming

The hallway usability testing is one of the twelve steps to better code proposed by Joel Spolsky; it goes

"A hallway usability test is where you grab the next person that passes by in the hallway and force them to try to use the code you just wrote. If you do this to five people, you will learn 95% of what there is to learn about usability problems in your code."

I never heard of such a simple yet smart trick before. Maybe because the hallway usability testing is a close relative of the combination of different XP (and not only XP) practices such as Test Driven Development, in which tests are the first users of your classes, pair programming with frequent pair rotating, in which you don't need to stalk the hallway to get somebody's attention, and collective code ownership, which causes everyone to shower insults at you (in a friendly manner, of course) when you deserve it.

That is another demonstration, should it be needed, that there are different effective paths leading to the same goal.