Has there ever been a situation where you wanted to bind a drop down list to a data source but also have a static item in there (i.e.: Pick One, Show All Cars, etc.)?  The AppendDataBoundItems property makes this a lot more simple.  Simply add your items at design time, make sure this property is true, and then also set your DataSourceId.  The static items you inserted will then not be overwritten when you bind the data to the control.