That will be the legal argument in court: is Apple's iOS like a specifically grocery chain that controls 20% of stores, and customers can easily go to another?

That will be the legal argument in court: is Apple's iOS like a specifically grocery chain that controls 20% of stores, and customers can easily go to another? That will be Apple's position. It seems clear that it's not, since I can easily bounce from store to store, and it's much more complicated (though by no means impossible) to switch mobile platforms. The other position also seems extreme: defining the scope of the market as "iOS users" would result in forcing Apple to make room in their store for everyone and everything, as if it weren't possible to seek alternatives at all. It's not an easy issue, but both starting positions seem extreme.