Based strictly on market share, out of 100 travellers with portable music/video players, 70 - 80 of them have iPods, with the remaining 20 - 30 having a variety of other players, probably not with the same plugs. What would you choose to support? You can never please everyone, so probably best to do what would most likely please the most amount of customers.

Should there be Zune-only plugs instead, so that perhaps only 2 out every 100 travellers with portable content can use the system?