everyone saying it's a bad technique, while it certainly SUCKS ASS compared to the proper methods of a pipe or glass tube........
If he makes the foil right, he doesn't need to 'run' it. and any efficient chaser can smoke this way like a charm.
IF I HAD TO DO IT THIS WAY first id get a 6" by 4" foil burn the chemicals off, make a sort of grove in the middle for the crack so it all essentially remains in the center (you may be thinking it'll burn, but hey this method sucks anyways so if he burns 25% of it, it'll still work good) and like i said, a tooter with a larger end toward the end that'll be sucking up the vapor/smoke , and keep that flame as far down frome the foil as you can to prevent burning, i think it should be atleast 60-75% as effective as the proper ways to use.
i don't think he should run it at all. i think the way i said, drop .1-.3 rocks whatever your prefference and then slowly smoke those trying to vaporize as much as possible but don't worry if it smokes from too much heat.... foil loses it's heat very quickly so you can drop large rocks id think and not worry about puttit it down for abit and going again with the same bit, but never use the same foil for more than 1 rock at a time due to, foil tends to.... actually decompose and it'll break and you dont want it breaking and losing a rock.
to answer the question. No the rock will not be wasted unless you fuck up the process, it will not be as effective, thats all.
i smoke plenty of crack, i'm not an expert but i know for a fact that this'll work good enough if he cant go out of his way for a stem or pipe.
i put my artistic abilities to the test and drew the toother aka straw that you should make out of foil, large end over the crack. i always used a tooter of this style to smoke heroin.