drop if exists

From time to time the suggestion crops up of allowing a DROP IF EXISTS 
... syntax. This seems not unreasonable, and I just spent a few minutes 
looking at what might be involved. Especially in the case of a table, 
view, sequence and index the changes look like they would be very modest 
indeed, and not enormously greater in the case of  a type, domain, 
conversion and schema.

Is this worth doing? Would it be acceptable?

cheers

andrew