True friends ABSOLUTELY will hurt each other! When two people are so close they are both the splinter and the salve.
Friendship has a "soul-bearing" factor to it. Without that vulnerability its really just an acquaintance. With that - well the other person has ammunition. It's how the balance is met that makes the difference.
No matter what - maintaining boundaries is important. Being a friend doesn't make a person the answer all the time. I find that for me to care for my friend I DON'T tell them everything sometimes.....why burden a person with all of your woes when he or she has their own? Friendship isn't an automatic door into another's life, nor is it a guarantee that they will be able to always enter your life. Like any relationship - friendship has it's limits.