Hi, unfortunately until J! 1.5 there is no way to do what you are requesting without changing core code.  Basically Joomla provides no way to tell the bridge that a user was deleted.  So there is no way for me to integrate that deletion to SMF.

In JSMF 2.0 it is recommended that you remove users from SMF, which will additionally remove that user from Joomla.  SMF is nice and provides an event that notifies us we should delete the SMF user.  If you use CB then I have written a plugin(to be released with JSMF 2.0) which does the same.  CB tells us that they are deleting a user, so we know to delete the SMF user and we do so. 

Basically, everything from SMF syncs to Joomla with JSMF 2.0.  Everything from CB syncs to SMF with JSMF 2.0.  Almost nothing from Joomla syncs to SMF due to the lack of events.  So use SMF or CB when managing your users.  Got it? 

well you won't have to wait for *future* releases long.  My testers are just double checking JSMF 2.0 Beta as we speak.  If everything is in order, it may be available tonight.

Actually, and you may find this more usefull, I DONT DELETE USERS AT ALL!

I simply edit the profile and overwrite the email, hint, and password fields with random garbage and turn off any notifications that that user is recieving. That way the continuity of your database is maintained.