ListView SectionIndex Example

http://docs.xamarin.com/guides/android/user_interface/working_with_listviews_and_adapters/part_2_-_populating_a_listview_with_data/

I've been over this all morning and I'm darned if I can see what the SectionIndex example is supposed to show me. I don't see sections appear anywhere when I run the app: not in the title bar; not as rows in the listview; not as an overlay when I scroll.

So what obvious thing am I missing here?

Testing on a 13" Note Pro using latest Jellybean.