I beleive in all intended purposes that the product was designed to work. Like jpappy said, it's possible that after so much handling through the distribution chain and storage of these products that many are no longer any good after reaching our aquariums. The directions on the bottle for most are designed to keep you as a customer returning and buying more, a steady source of income. What good is a product that you only use once right?
I used it when I first set-up my aquarium as well. I didn't add any fish to it, was going through a fishless cycle. It took 6 weeks for the tank to fully cycle, so I would have to say that the product failed me. As with many of these marketted products, I won't be surprised if they have a combination of things in there that puts our fish on "life-support" to allow us to think that the product is doing it's job. Products like Prime, and Stress-Coat, Ammo-Lock, or even Salt will all do the same thing, de-toxify on a temporary basis, giving customers the illusion that it's working.