you could set the system to fire out an email at every month of contunued total lack of activity. saying something like;
"We have noticed you have not yet posted to the EvC forums after -N- days. Click here to visit the EvC Forums.
or Click here to deleate your EvC Forums account"
after three concecative unanswered massages assume a DNA (Dead Never Active) and loose the account.
Woulndt auromatically deleate the account just fire a message to the admins to do so.