MongoCSharpDriver deserialize anonymous type

TempDataDocument

public class TempDataDocument
{
    	[BsonRepresentation(BsonType.ObjectId)]
	public string Id { get; set; }
	[BsonElement("key")]
	   public string Key { get; set; }
	[BsonElement("value")]
	[BsonSerializer(typeof(CustomSerializer))]
	   public object Value { get; set; }
}
	
public class CustomSerializer : IBsonSerializer
{
	#region Implementation of IBsonSerializer
	
	public object Deserialize(MongoDB.Bson.IO.BsonReader bsonReader, Type nominalType, IBsonSerializationOptions options)
	{
		return Deserialize(bsonReader, nominalType, null, options);
	}
	
	public object Deserialize(
		MongoDB.Bson.IO.BsonReader bsonReader, 
		Type nominalType, 
		Type actualType,
		IBsonSerializationOptions options)
	{
		if (bsonReader.GetCurrentBsonType() != BsonType.Document) 
		{
			throw new Exception("Not document");
		}
		
		var bsonDocument = BsonSerializer.Deserialize(bsonReader, typeof(BsonDocument), options) as BsonDocument;
		var cleanJson = Regex.Replace(bsonDocument.ToJson(), @"ObjectId\((.[a-f0-9]{24}.)\)", (m) => m.Groups[1].Value);
		return JsonConvert.DeserializeObject<object>(cleanJson);
	}
	
	public IBsonSerializationOptions GetDefaultSerializationOptions()
	{
		return new DocumentSerializationOptions();
	}
	
	public void Serialize(MongoDB.Bson.IO.BsonWriter bsonWriter, Type nominalType, object value, IBsonSerializationOptions options)
	{
		var json = (value == null) ? "{}": JsonConvert.SerializeObject(value);
		BsonDocument document = BsonDocument.Parse(json);
		BsonSerializer.Serialize(bsonWriter, typeof(BsonDocument), document,options); 
	}
	
	#endregion
}
	
void Main()
{
	var client = new MongoClient("mongodb://localhost:27017");
	var server = client.GetServer();
	var database = server.GetDatabase("mvc");
	var collection = database.GetCollection("tempdata");
	var document = new TempDataDocument()
	{
		Key = "key1",
		Value = new 
		{ 
			Nombre = "Sergio", 
			Twitter = "@panicoenlaxbox"
		} 
	};
	collection.Insert(document);
	var data = collection.FindAs<TempDataDocument>(Query.EQ("key", "key1"));
	Console.WriteLine(data);
}

Yo si que tengo el Id:

/* 0 */
{
"_id" : ObjectId("537b23be3814fe25e8119e01"),
"key" : "key1",
"value" : {
"Nombre" : "Sergio",
"Twitter" : "@panicoenlaxbox"
}
}

/* 1 */
{
"_id" : ObjectId("537b4e733814fe181cd96417"),
"key" : "key1",
"value" : {
"Nombre" : "Sergio",
"Twitter" : "@panicoenlaxbox"
}
}

/* 2 */
{
"_id" : ObjectId("537b4e753814fe181cd96418"),
"key" : "key1",
"value" : {
"Nombre" : "Sergio",
"Twitter" : "@panicoenlaxbox"
}
}

Y no me salta ninguna excepción :(

Pues llevas razón, error mío, luego actualizo el post con una super-mención para un tal lurumad :)
Gracias