Effect of Frost/Freeze on MJ Plants?

Can anyone tell me the specifics of the effect of frost/freeze on an outdoor plant? A friend didnt harvest his plants and left them thru like 4 days of frost/freeze. Some of the leaves look dead. The buds dont look real bad. What will his smoke turn out like, is it gonna taste bad, not get a person high, be less potent? Book says dont put processed pot in freezer, but gives no reason. I remember reading somewhere here that freezing explodes the cells of the plant, but what effect will that have on the product?

Thank You