attaching death certi for particular user could be useful to close particular account.. i guess it really works..
I wonder why you are worrying about dead people. Dead people wont create any load on Facebook servers. Facebook uses various caching techniques. Eg: If you login to Facebook after few days, you won't see up to date wall. You need to click most resent link to update wall... So dead won't create any kind of a load on Facebook servers.