Yeah what is it with people throwing "monopoly" at everything? Just because they're an industry leader doesn't mean they're anything close to a monopoly.
Is not the only, nor even the most useful, definition of a monopoly. And there's also not a magic moment where one second you're not a monopoly, and the next second you are when user X+1 signs up. It's a gradual process and that's why it is such a huge area of law.
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