Drubin's right about double-blind: it means that nobody in the room knows which is which. And researchers use it because they've learned that there are all sorts of ways that someone can subconsciously indicate which is which to whoever is actually doing the comparing. If you want to be absolutely sure that there's no outside influence (intentional or not) and that you're making your decisions based only on the sound, double-blind is essential.
That said, the main reason DBTs are controversial is that they tend to produce results that are at odds with the received wisdom of audiophilia.
That said, the main reason DBTs are controversial is that they tend to produce results that are at odds with the received wisdom of audiophilia.