JSON.NET "System.OutOfMemoryException" when deserializing into a DataSet

I'm not at all familiar with DataSet, but after playing around with it a bit, I think I've found the reason. According to the documentation:

The DataSet consists of a collection of DataTable objects

Because a DataSet is a collection of objects, you can only deserialize a collection (array) into it. So,

{"items":[{"id":"1122267","quantity":"1","bundle":"1"}],"seconds_ago":"1"}

will not work, because it contains one collection (of items) and one property (seconds_ago). On the other hand,

{"items":[{"id":"1122267","quantity":"1","bundle":"1"}]} 

works, because it only contains one collection.

Therefore, if you really want to deserialize your json string into a DataSet, you should do this instead:

{
    "objects": [
        {
            "items":[{"id":"1122267","quantity":"1","bundle":"1"}],
            "seconds_ago":"1"
        }
    ]
} 

You should really consider deserializing into a C# object though, which in my opinion is less complicated and easier to handle:

public class RootObject
{
    public List<Item> items { get; set; }
    public string seconds_ago { get; set; }
}

public class Item
{
    public string id { get; set; }
    public string quantity { get; set; }
    public string bundle { get; set; }
}

RootObject deserializedObject = JsonConvert.DeserializeObject<RootObject>(json);