[limey]

BigV, you don't know when someone is considering suicide, especially if they really mean it. If you're lucky it is a cry for help and they choose a method that allows an escape route. But if they are determined to kill themselves then they'll do it and all you can do is wonder why, and what if ...
I think Bri is right, it is a selfish act, and one caused by illness. But that doesn't mean to say that you could do anything about it even if you were aware of what a suicide is planning.
My internet research on the subject indicates that the relatives of a "successful suicide" are more likely to kill themselves, too: somehow the fact of a suicide in the family makes it a more viable option. My experience tells me that once you've seen the train-wreck that a suicide makes of the lives of those that loved that person, it's the last thing you'd do.
Wolf, comments?