Service element question

[Victor Grey <victor@idcommons.org>]

The latest editor drafts of Res 2.0 WD10 state that the Service element 
of an XRD has a priority attribute, because "there can be more than one 
instance of a particular service type for redundancy".

It's a small point, but since a Service element distinguished by a 
particular combination of Type|MediaType|Path elements can have n-URL 
elements with priority attributes, what is the case where you would 
want instead to have more than one Service element with the same 
Type|MediaType|Path elements?

=vg