This is like the best idea after inventing cremation :)
I can imagine some problems, as it would be very easy to steal the defunct.

http://gizmodo.com/5468152/a-screw+in-coffin-is-clever-and-economical

screw-in-coffin

P.S. The first comment made me laugh – in case it gets moderated, here it is:

The5thElephant 11:21 AM
Only necrophiliacs like to screw in a coffin.