Think of it as the modern day equivalent of an "I voted" sticker.
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Facebook is tracking users who sound off about casting their ballot in the midterm elections today, and put the results in an interactive map that updates in real time as more people share with the social network that they voted.
So far, it appears that most people are voting -- or at least clicking the "I voted" button on Facebook -- in the Northeast, particularly around New Jersey, according to the map. But that could change as it gets later and the West Coast starts heading to the polls.
More than 4 million people have clicked the button today, Facebook said.