No explanation is given as to why Emma can see her future Facebook page, but it has always been my personal philosophy that if you give me a premise I will go along. I only have problems when you stray from the original premise.
Facebook is used here as a way to make these two characters think about what they are doing in the present. Knowing what could happen to them in their futures is powerful and confusing. Should they look up their friends to see what happens to them (and then tell them)? Should they stop looking at Facebook once they realize their current day actions can actually change their future lives? Emma and Josh deal with these questions and a lot more (including the romantic tension between them).
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