What's missing from this (and most "why $newcomer will beat $incumbant" claims) is why Facebook can't simply duplicate the feature, and remove it as a different

What's missing from this (and most "why $newcomer will beat $incumbant" claims) is why Facebook can't simply duplicate the feature, and remove it as a differentiator. As a programmer, and looking at what Facebook can do already, it just doesn't seem like adding a "let everyone from my *.edu see this" permission level would be that hard.