Since someone linked both standards elsewhere in the thread, this is the first valid, self-contained example XML document appearing in the XML spec:

    <?xml version="1.0" encoding="UTF-8" ?>
    <!DOCTYPE greeting [
      <!ELEMENT greeting (#PCDATA)>
    ]>
    <greeting>Hello, world!</greeting>

The first example of a complete, self-contained yaml document in the yaml spec looks like this:

    # Ranking of 1998 home runs
    ---
    - Mark McGwire
    - Sammy Sosa
    - Ken Griffey
    # Team ranking
    ---
    - Chicago Cubs
    - St Louis Cardinals

I think that is quite representative of the user experience as a whole: Yes, there are a ton of dark corners in Yaml that only a tiny fraction of people truly understand, but the default user experience feels just like writing a slightly more convenient JSON, whereas XML by default is a garbled mess.