I have actually asked this question here a while ago. Here is the actual thread with various suggestions:
http://www.linuxquestions.org/questi...-slack-885710/
As per my last answer, after checking the FHS specifications, I decided the /srv/samba would be pretty much the right place. /home (as some suggest /home/samba or /home/pcguest) seems to be specifically for users with local credentials, not for a daemon supplying data to the rest of the world (at least as far as I can understand it) - so /home/samba is out from where I stand. Also, because FHS recommends that there should be no new folders created directly under /var (/var/samba would have been my next favorite location) - that is out as well. So it seems /srv/samba might be an appropriate location.
As far as /mnt is concerned, it seems to me that's where mount points for filesystems mounted *by* the local system should be, not filesystems exported by the local system.
Well - that's as far as I can figure it out. It still seems a debatable issue though.