I saw the same thing right away. Seems like the first item in the array would have to be used as a hash of key/index pairs to be used for the following items. I guess this would only be useful with large sets of data, the examples makes them look kind of silly =)

So this:

    "users": [
        {"first": "Homer", "last": "Simpson"},
        {"first": "Hank", "last": "Hill"},
        {"first": "Peter", "last": "Griffin"}
    ],

Becomes:

    "users": [
        ["first", "last"],
        ["Homer", "Simpson"],
        ["Hank", "Hill"],
        ["Peter", "Griffin"]
    ],