Mark Newton, the engineeer from Internode over whom a bit of a storm developed last year over (incorrect) accusations that Minister Conroy's office had heavied IIA to have him curtailed, has written to Policy on the subject. Policy is the magazine of the Centre for Independent Studies, a leading laissez-faire think tank.
I haven't usually associated it with the libertarian bent though, I would think its sponsors are more from the socially conservative right. The problem with Mark's analysis is that he again assumes that once Senator Conroy has proven the ability of a blacvklist website filter that all other aspects of the regme stay the same.
I suspect that were there to be success on the blacklist filter technical trial some of the other issues would be easier to deal with. This includes changing the rules to provide more accountability on the generation of the blacklist.
Finally, a little note because onroy's line about the purpose of the filter being about "protecting children" has been interpretted as being about protecting children from seeing the images - it isn't. It is about protecting the children who are the subject of the images.