I was working as sysadmin when our solaris cluster hosting 18 Oracle instances went crazy when someone filled the /tmp mounted as tmpfs (Solaris standard) with stupid log files turned to DEBUG level.
Oracle instances simply stopped to work (messages like not enough memory to fork) and Sun Cluster did not understand the situation and all resource groups went in STOP_FAILED (aka "I don't know how to handle... good luck to you!").
I really think that the default should be the safest choice available and, when needed or desiderable, is sys admin responsibility to look for performance optimization as tmpfs clearly is.
Maybe a simple package to install? yum install tmp_on_tmpfs