It's an interesting idea, but I don't think Musk understands the U.S. constitution well enough, this is certainly a good idea for other countries. The U.S. was built specifically to stop any chance of mob mentality. Many might find it interesting that many years ago you have to own land to vote. The idea behind this is that the poor will always exist and if they get to vote they will always vote to take from the "haves" and give to the "have not's". This societal truth is why democracies turn into socialist governments, then revolt and then back into Republics. Very interesting to watch this process that occurs in every country. The U.S. is actually now changing from a Republic to a Democracy; this is a long process, but once complete the transition from Democracy to Socialism will be very quick. The move from Socialism back to a Republic may never happen though, because the U.S. have such a strong military that could just used very effectively by a dictator/socialist leader.
RE: Elon Musk advocates Direct Democracy