http://developers.de/blogs/damir_dobric/archive/2012/02/28/emitting-empty-values-with-asp-net-webapi-json.aspxSometimes you will have complex type which have many properties. Statistically in this case some of properties in some request will not be used. If you have operations which use lists in contracts it is clear that transport of none-used values will increaseenCommunityServer 2008 SP1 (Build: 30619.63)