By the way the diode option is a decent one too, I went for this option because I had many 12V PSUs around, and due to the efficiency of the converter I can use ones with pretty low amperage. But if you have a decent 5V supply using a simple diode drop is not a bad option.

What is bad is using a resistor as the voltage drop will depend on the current being drawn by the device, but the article is not doing that (nor woudl I).