In most cases, you see that the curses can't even be removed by even the ones who curse others. It's not really clear as to those guidelines. It is a rule of thumb, I believe, that there isn't anyone alive capable of such things.
It used to be, to some degree, that you would have two names. One name was kept private and never spoken to anyone. The other, your public name. The idea being that those with your birth name could have enough to know when to attack you, trade with you, what have you, and come out ahead. That's not really a curse but it gives you an idea of what used to happen and the closest thing to a curse than can be done today.