Within the relational database world, you can do precise, structured queries against specific fields in your tables. In a properly normalized database, this is all-powerful.
However, when you bundle a bunch of content up in an XML package, and stuff that into a single field, you lose this functionality of doing atomic searches against those fields. In the example I wrote up—a geocaching XML record with latitude, longitude, etc.—there would be no way to this type of query:
SELECT * FROM content WHERE longitute BETWEEN -122.5 AND -120.5;
So, a problem. A big problem, since searching data is a pretty fundamental concept in content management—hell, in any application. I have some ideas that address this, but they’re still percolating. More to come.