Apart from dense tropical woods, such as ipé or jatoba, it does not hurt wood to heat treat it. (You can 'boil the oils' out of dense tropical woods and cause drying checks.) Some woods just benefit more from a heat treatment than others. Sure, you CAN heat treat yew, osage or black locust without ill effects, but the benefit is just lower than with most whitewoods.
Bow101 asked if I heat treat every bow I make. I simply replied 'no', based on the woods I work with most of the times. If I made only hazel bows, my reply would be 'yes'.