One of the new features in .NET 3.5 SP1 is WCF serialization support for "POCO" types (plain old CLR objects) that don't have any [DataContract] or [Serializable] annotations (similar to XmlSerializer behavior). You can read more about it on my blog here: http://www.pluralsight.com/community/blogs/aaron/archive/2008/05/13/50934.aspx