None of these are the real problem with the hyperloop. The real problem is how an infrastructure-heavy, point-to-point system can possibly compete with personal vehicles that can go just about anywhere–the United States has more than 4 million miles of public roads–or with an airline system that requires very little infrastructure and can serve far more destinations than the hyperloop.
Musk promises the hyperloop will be fast. But fast is meaningless if it doesn’t go where you want to go. Musk estimates that people travel about 6 million trips a year between the San Francisco and Los Angeles urban areas, where he wants to build his first hyperloop line. But these urban areas are not points: they are huge, each covering thousands of square miles of land.
Airlines deal with these large areas through multiple airports. The Los Angeles area has five commercial airports and San Francisco has three. The hyperloop would only have one station in each region, making it inconvenient for the vast majority of people.
Moreover, airplanes from these airports can reach hundreds of other airports across the country and around the world. Even if Musk’s optimistic cost estimates are valid (and remember, the first cost estimate for California high-speed rail was about $10 billion, less than a tenth of the current estimate), the hyperloop would require billions of dollars spent on more infrastructure to add any new city.