It would be nice to have option to bind ComboBox to data on client (javascript array). In case you have 2 ComboBoxes using same list of items, combos call server method 2 times.
Binding combos to client js array is supported when using pure Kendo UI client widgets. Regardless if you use the client widget or the MVC wrapper, when you feed two combo instances with data through a method it will be called 2 times. In case you want to have support for shared data source in the MVC wrappers, cast your vote for this feedback item: http://kendoui-feedback.telerik.com/forums/127393-telerik-kendo-ui-feedback/suggestions/3210033-allow-use-of-shared-datasource-for-multiple-contro