Yes, the order-obessession of XML is a constant source of surprise in XML. The idea that

   <myObj>
      <Foo>myFoo</Foo>
      <Bar>myBar</Bar>
   </myObj>

is somehow different from

   <myObj>
      <Bar>myBar</Bar>
      <Foo>myFoo</Foo>
   </myObj>

is incredibly surprising and frustrating, and XML schema actually supports ignoring the difference but xml schema tools seem to hate using the "all" instead of the "sequence" schema definitions.

The worse offender, imho, is Microsoft's DataContractSerializer, whose default behavior is to silently ignore this ordering failure and also silently fail to deserialize any out-of-order elements.

Either fail loudly or be flexible about ordering.