/var, /var/tmp ?

Hi, Quick one. I have a multi-user system and the directories /var and /var/tmp are both r/w all users. /var/tmp is mounted in the /var slice with the same privs. Should I make a separate /var/tmp partition to stop users filling it up with crap and stopping the proper function of /var? Also, is there anywhere else I should know about with this problem? Alternatively, should I set quotas? All the users are responsible apart from a couple! Cheers, - Chris.