I wouldn't want anyone to and tbh the only person who would have a chance in hell of using my account is on here anyway. If they felt it necessary they can create their own account on here to tell people.
i think there's a policy on this, maybe one of the moderators can answer. you can't have anyone login as you and post, even if you are gone. your friends/family would need to setup a new account and post separately.
as for letting people know, yes, i'd want my friends here to know. hopefully it won't come to that, though.