Temporary files: RAM or disk?

The entire thread have arisen because /tmp on tmpfs brings no speed. It brings problems, but no speedup to default real-world use cases. "What's so good in /tmp on tmpfs?" was the main question of the thread. Not just "why tmpfs is good", but "why /tmp on tmpfs is good".

You can put this questions as "Why /tmp on tmpfs is better than /var/ram on tmpfs?"

The only point that nobody objected to is that it's better to put /tmp on tmpfs than on a very small or read-only root partition. But that's not a problem for debian, where someone smart implemented a TMP_OVERFLOW_LIMIT feature, that automatically mounts tmpfs over /tmp if there's not enough free space there or root fs is read-only.