I’m inclined to agree with you that organizations like schools and corporations have the right to use filtering software, but it’s not advisable. Many a school project has involved internet research that, for some reason or another, brought me to sites that were blocked for ridiculous reasons: a project for German class, for instance, involved picking a German city (mine was Köln) and, among other things, listing popular restaurants; the sites for many of the restaurants were blocked for “Alcohol”, which they presumably served.

There’s nothing of the sort of the New URL block, though, in the software that I’ve encountered, nor blanket blocks on blogs. I’ve additionally found the moderators to be responsive, to an extent: YouTube was blocked for a few months, the block ending under protests by student and the teachers who often found it convenient to use the site as a source of demonstrations, media clips or whatever the case may be.

In addition, from my experience, someone recently has managed to slip Chinese proxy software–you know, the kind developed to circumvent the Great Firewall–on the public drives, thus blunting the effects of block lists. Only a few people noticed at first, and the software is periodically deleted and reuploaded, so in some ways it’s as gradual as a transition can get, and there haven’t been problems relating to the proxy really.