When you do this, I believe you get the experience from decons but not the materials if your crafting level isn't sufficient. For example, if you have not put any points into BS and you decon a steel or dwarven sword, you wont (or maybe just less likely?) to receive the mats, but you will still receive IP (inspiration points).

So it really ins't wasted because you have some return, but you don't get the full value of deconing.

Edit: Also, you might get more of a response by posting this in the Crafting sub-forum. This one is mostly for combat skills.