We don't use only PWB. Danny_B made some work recently so that all dumps
are in the same place etc., what consumed the most space were
duplicates. This was supposed to be documented on
https://wiki.toolserver.org/view/User-store but it's never been.
Most space is taken by view stats whose compression is discussed here:
https://wiki.toolserver.org/view/Talk:User-store
Nemo