Multiple rdf:type elements

An example of an rdf:Description element containing multiple rdf:type
elements came up in a recent discussion.  Clearly the syntax allows this,
and any one of the rdf:type elements could be used to produce a typedNode
form.

Has there ever been any discussion about the utility or meaning of this?
Perhaps to model multiple inheritance? Is it an oversight in the syntax?
Should RDF implementations complain about it if they have a checking mode?

Alan Lillich
Adobe Systems