These factors, along with the secretiveness with which the filtering
companies tend to treat their blocking lists, create an untenable
situation.  Especially when such filters are being used by public entities
such as libraries and schools, they create the Orwellian atmosphere of secret
censorship committees, completely devoid of any genuine accountability.  What
do the block lists really contain?  Porn sites?  Religious sites?  Political
speech sites?  We can't know if the lists are unavailable.  This is a horror
in any modern public policy context.  At a bare minimum, public institutions
should be prohibited from using any filtering software which does not make
its complete block lists available for public inspection!

Most manufacturers of filtering software are very serious about keeping
their lists hidden.  In a very recent case, individuals who decrypted the
block list from one such package are being sued by the company involved, who
is also reportedly trying to learn the identities of the persons who accessed
those decrypted materials from related Web sites.  While the detailed legal
issues relating to the actual decryption in this case may be somewhat
problematic, the intolerable fact that the block lists are kept hidden
seems to have at least partly driven this situation.