I just found out that one possibility is to grep all log entries associated with a specific subdomain on the fly and subsequently letting webalizer analyze that file:
"cat /var/log/httpd/access_log | grep -i foo.com | grep `date '+%d/%b/%Y'` >> ~/foo.access.log; webalizer -c ~/foo.webalizer.conf"
It "kinda" works. It's weird though that people that retrieved a page generated "Pages" but not *always* "Visits"! Is it possible that the grep command doesn't get all the necessary log entries for webalizer?