Would a non-zero number of people use the store? Of course. But voluntarily, and with the realistic option not to, which isn't tied to their choice of hardware or operating system.
And enough people wouldn't that Facebook would still feel a lot of pressure to have their app in Apple's store under Apple's rules, or at least some store and some set of rules that the users actually trust.
And enough people wouldn't that Facebook would still feel a lot of pressure to have their app in Apple's store under Apple's rules, or at least some store and some set of rules that the users actually trust.