Innominate: I don't think anyone rational believes in mandatory filters at libraries. Laws like that pass because the vast majority of the country are idiots, ignorant of the impossibility of blocking 'inappropriate' sites.
You are wrong. Things are only impossible in public (read - government-run) facilities. Private organiations would have no problem blocking any inappropriate sites if they cared.
Such service would have been easy to provide by a private company and probably exists already.
miko