I feel pretty conflicted on this. The way Trump is using his Twitter, it almost becomes public property. I mean he's making huge announcements, almost solely on Twitter. So, at that point, it's almost like denying public access to the State of the Union. But, on the other hand, it's his damn Twitter and he should be able to do whatever he wants with it. I guess it begs the question, when you're a "public servant", an…
Public figures have different standards of privacy. For example, the standard for what a news publication can report about you are different; thresholds for slander are higher.
What is a public figure? AFAIK, it's someone who voluntarily puts themself forward as one. For example, a movie star, someone who makes public speeches, etc. Running for President of the U.S. is volunteering to be the most public figure in the world, and arguably Trump seeks publicity beyond any other president.