In general I think if a DT member dies, his trust is still valid and I don't see a reason why it should be deleted.  The only exceptions to this are cases where someone might have successfully appealed the neg.  For example, if I suddenly died and one of the members I'd tagged for account selling had somehow turned into an extremely trusted member, then my feedback should be removed.  That's the kind of case which would have resulted in a successful appeal for me to remove it.

What happens when a DT member dies and no one knows about the death?  If it's a DT1 member, the lack of activity would remove the DT1 weight of the feedback, but he'd still be DT2 if I'm not mistaken.  It's a valid issue since a lot of members here don't really know each other and wouldn't really be aware that someone died.  Zepher was an exceptional case because he was active in a tight community like the collectibles one, but for a typical scam-tagging DT member?  It's not very likely someone would become aware of their passing IMO.