Yahoo's policy is different from GMail's. In GMail's terms it says they will hand over the account to the next of kin if you send them the death certificate, or if you have power of attorney over that person. Yahoo won't give access under any circumstances, although that's obviously over-ridden by the court's decision.

I found out about this was thinking about social media sites and how they're affected by death recently, which I did as a BarCamp talk and wrote up here:

http://www.paulsilver.co.uk/blog/2008/10/death-and-social-me...

I think there's stuff that should be in web applications that we miss because we don't think about death, i.e. should we have an extra e-mail for the next of kin of a user? (or effective next of kin in this context.)