Another approach is:

HISTFILE=$HOME/.histfile.$$

which create unique histfile for each login shell. In this case, problem is that user don't see his history from previous log-in and you have to delete this files during log-out process.

If you use csh [and clones], put

rm $HISTFILE in your .logout

If you use sh [and clones], try something similar in your .profile

trap 'rm $HISTFILE; exit' NULL