In the example here http://www.salesforce.com/us/developer/docs/pages/Content/pages_controller_lifecycle_example.htm?SearchType=Stem&Highlight=Setter|setter|setters, can someone explain why selectedValue = value; is a side-effect? Why cannot you set selectedValue in its own setter method?

public class componentController {

    public String selectedValue {

        get;

        set {

            editMode = (value != null);

 // Side effect here - don't do this!     

            selectedValue = value;

        }

    }

    public Boolean editMode {get; private set;}

}