Comment: The problem with ballot selfies is that they allow for the possibility—an unlikely one at the moment, perhaps, but our country does have a history of this sort of thing—of an outside party using them to verify that they have cast their vote in accordance with outside pressure of either a positive (e.g., if you vote for this person I'll give you fifty bucks) or a negative (e.g., vote for this person or else I'll fire you) nature.

That's the reason a number of states have bans on showing others your ballot—and also the reason that such laws are not in any way stupid.