[3pt14159]

The problem with YAML is that meaningful whitespace means that the size grows quickly for highly nested documents. I don't love XML, but there is a reason I recommended Ox. I've used it for real projects and it never fell over like so many of the alternatives I've tried where databases were not in the cards.

[fny]

The problem with XML is that angle bracket expressions take up too much space because you need to duplicate element names. I don't love JSON, but there is a reason I recommend OJ.

...

The problem with JSON is that the keys take up too much space because they are duplicated. I don't love BSON, but there's a reason why I recommend bson-ruby.

And I could keep going... ;)

The benefit of using YAML is precisely that there's meaningful whitespace. Different strokes for different folks.