Unlike with other applications where, by the time whatever data is being exchanged reaches the wire, it's no longer expressed as bulky and bandwidth-inefficient text, the text-based nature of XML traffic raises questions about the potential for network congestion and response time of transactional systems that must parse any XML-based data before figuring out what to do with it. Picture a highway full of tractor trailer trucks (as opposed to motorcycles) with on- and off-ramps that aren't perfectly equipped to handle heavy truck volume. The opportunity is ripe for congestion that affects more than just the XML-based traffic.
LaMonica's story touches on various approaches being considered by vendors as well as the World Wide Web Consortium (W3C) which has formed the Binary Characterization Working Group to consider putting XML in binary format. As a side note, W3C working groups are no guarantee that there will be a standard. Like any