title: Why is Serializable Attribute required for an object to be serialized
body: <p>Based on my understanding, SerializableAttribute provides no compile time checks, as it's all done at runtime. If that's the case, then why is it required for classes to be marked as serializable?</p>
  
  <p>Couldn't the serializer just try to serialize an object and then fail? Isn't that what it does right now? When something is marked, it tries and fails. Wouldn't it be better if you had to mark things as unserializable rather than serializable? That way you wouldn't have the problem of libraries not marking things as serializable?</p>