[ygra]

Isn't CDATA character data anyway and thus not even binary but in the document's character set? Which makes it a poor choice for binary data even without taking into account that XML forbids certain characters.

As for binary data in web services ... isn't it easier to just use Content-Type for that and use the appropriate type for the payload? That wouldn't require a textual data format that can contain arbitrary binary data.

[derefr]

That presumes you want to send a lot of binary data. Sometimes you just have five bytes or so. (E.g., as in the article, an un-decoded string.)

(Still, you're right, I admit to having been able to avoid any work painful enough to teach me XML arcana. I was actually thinking of one of the many variants of "Binary XML" I had read about recently, and assumed the typing was bijective to XML's own types. In other news, BSON of all things has a raw-binary type.)