Should my Azure DocumentDB document classes inherit from Microsoft.Azure.Documents.Document?
This behavior is attributed to how JSON.NET deals with properties on dynamic objects. It effectively ignores them unless you decorate them with the JsonProperty attribute.
You can either work with plain POCO or you can extend from Resource (shown below), which is a static object that Document itself extends.
public class Person: Microsoft.Azure.Documents.Resource{ public string Name; public int Age;}