The things that bother me the most about thunderf00t's video are:
1. Sure, expansion, fine. WHAT ABOUT YOUNG'S MODULUS, YOU RETARD? Steel is flexible! It is certainly not a fagot of strands, as his expansion diagram would suggest.
2. No discussion about actually solving the "show stoppers". Example: rust is trivially* solved by merely switching to stainless steel.
*At no small cost, mind, but it's trivial on the drawing board. Somewhere inbetween lies the real answer. Galvanized or aluminized steel for example, or just good old paint.
Flex is a particularly bothersome issue, because he's mentioned it several times, yet he still hasn't realized the existence of actual pipelines crisscrossing the continent already. It's a solved problem.
Now, not necessarily that it's solved on precisely the same scale, no. Most of those pipelines are filled with a fluid (water and petroleum being the most important), which keeps the temperature consistent across the pipe and from day to day.
But then, there are pipelines crisscrossing major fault lines, subject to Earthquakes at least as strong as California has ever seen, that see enormous seasonal temperature swings: Alaska. And they're fine. They solved that by giving lateral freedom on the supports, and zig-zagging the pipeline across the countryside.
A "Hyperloop" would have to have much softer bends in it, because of its contents; but there's no on-the-face reason that this factor is a complete game breaker.
Tim