Quote Originally Posted by hobbes
Whenever data is transferred between disparate systems, it must be structured in some way that is understandable to the communicating systems. Structured information contains both content and some indication of what role that content plays. Tags provide structure and meaning to data.

The article does not propose an alternative approach to data transfer that provides the key advantages of XML - flexibility, simplicity, interoperability - without the use of tags. It is the problems faced by older complex data transfer mechanisms like EDI that led to the evolution and increased acceptance of XML.

Bottomline: The benefits of using XML in the right context outweigh the extra storage space it takes up in the database.
You make a good argument for the use of XML as a data transmission/exchange format, which is what it is really useful for, but that is a matter independent of how the data is stored in the database. I don't recall anyone seriously arguning against the use of XML as a data exchange format, although it does have some disadvantages that ought to be acknowledged, whereas inside a database it is practically impossible to enforce consistency on it (data lengths, formats, foreign keys etc) without going to more trouble than you would experience in storing it relationally.

An RDBMS is not just a data dump.