Justin Timberlake got into some trouble because he took a selfie photo in the booth when he went in to cast a ballot via early voting. As this article notes, that's illegal in many states. [Caution: Link may play noisy video when you get to that page.]
Back in 2015, I explained why this law doesn't make sense to me…and I even postulated then about something I never thought anyone would ever do: Voting for Donald Trump in a national presidential election. Briefly though, the premise is that by making it illegal to take such a photo, you make it harder for someone to sell their vote. But it doesn't since there are so many ways around it.