I'd like to say that they give you special powers, or special privileges, but really they're only a souvenir of the cruise, and may help you identify another DISBoard cruiser.
However, my DW and I have two we got on the 2010 WBTA cruise, and as they glow in the dark, we take them with us when we travel, and use them to identify the bathroom door in a hotel or on a cruise at night.
Hey! How about this: Anyone who takes one undertakes to distribute pixie dust to someone else on this cruise? It can be a CM, another DISBoarder, or just anyone. What do you think? I'm big on pixie dust, have being on the receiving end on previous cruises.