Obviously, there are no thermal considerations of running these fully loaded. None whatsoever. Nothing even remotely warm here, move along.
In their defence, at least the drives themselves will generate reasonably even thermal load; no more ahead-of-the-MTBF-curve "top-slot failures" as you'd get in a conventional vertical stack.
The internal airflow & insulation is gonna have be stunning to stop the devices in the U's above getting it in the soon-to-be-very-warm shorts, mind. And I doubt it, if the pics are anything to go by.
Flames...well, it's obvious innit.