Where XML goes astray... and when you should or shouldn't use it

First, some background: XML was originally designed as an evolution of SGML, a simplification that mostly matched a lot of then existing common usage patterns. Most of its creators saw XML and evolving and expanding the role of SGML, namely text markup. XML was primarily intended to support taking a stream of text intended to be interpreted as a human readable document, and delineate portions according to some role. This sequence of characters is a paragraph. That sequence should be displayed with a link to some other information. Et cetera, et cetera. Much of the process in defining XML based on the assumption that the text in an XML document would eventually be exposed for human consumption. You can see this in the rules for what characters are allowed in XML content, what are valid characters in Names, and even in "" being required rather than just "".