Why I am against the Internet Filter

No, I'm not a great lover of pornography. Our governments should take active steps to reduce the pervasiveness of pornography in our society. It's simply that the Internet Filter is not an effective way to do it.
The arguments against the Filter I will discuss here are purely pragmatic. In summary, the Filter will inhibit internet performance and user experience and does not address the primary given reasons for its implementation. Additionally, the filter will allow for the suppression of free speech. It has already proven so in the trials conducted with a handful of ISPs, as the 4 Corners program on the Filter this week showed.

The Filter will inhibit Internet performance

The Filter does and must work on the level of domain names and URLs, the character-based addresses you type into a browser address bar and click in hyperlinks. These domain names are mapped to numerical IP addresses that can be quickly and easily changed. Therefore the only effective way to filter illicit material on the internet is at the domain name level, not at the numerical address level.
Unfortunately, the transmission of messages over the internet relies purely on the numerical addresses. Packets of Internet information must be aggregated and decoded in order to ascertain the URL. This produces a performance overhead that simply must slow down performance when implemented on a massive scale at every ISP. The performance may not be visible to users viewing Web sites in browsers, but will impact on the rapidly increasing use of World Wide Web protocols to transfer data between businesses (Web Services).

The Filter does not deliver its promise

The primary reasons given by the Government for the Internet Filter is to protect children from pornography and to stop the distribution of illicit pornography. It cannot deliver on either of these promises.
There is a proliferation of proxy and tunnelling services available on the internet to bypass school and corporate firewalls and country firewalls such as China's. Simply googling “proxy bypass” returns a multitude of options. These services will work equally well with the Internet Filter. If children want to access pornography on the internet, then ISP-level filtering will not stop them. Only software installed on the user's computer can effectively perform this function.
As was discussed in the Q&A discussion accompanying the 4 Corners program, only a tiny fraction of the distribution of illicit pornography on the Internet is via the World Wide Web, the only part of the Internet that would be filtered. Illicit pornography is distributed on peer-to-peer (P2P) networks and virtual private networks (VPNs). The only way to investigate and stop the use of these networks to distribute illicit material is to actively infiltrate and gather evidence against the people who use them for this purpose. World police forces already have large sections devoted to this purpose and are doing the best job they can. While the number of arrests and prosecutions is currently small, they will grow as police gain the experience and technical skills they need to better infiltrate these groups.

The Filter will suppress free speech

An unfortunate consequence of government censorship is that the bureaucracies established to enforce it will always be slow to react to new threats and slow to react when something goes wrong, such as the accidental blocking of a legitimate Web site. Rules and policies established by regulatory authorities over time become divorced from the values they are supposed to enforce. How often have you heard a bureaucrat state that the “rules are the rules” and that there is nothing they can do to change them. If you've ever had dealings with the ATO, ASIC or other government bodies, you will have heard words to this effect. Even when there is no logical reason to enforce the rules in a particular instance or when it is arguable that the circumstances fit the particular rule being applied. Bureaucrats will usually respond to the legitimate fear that use of discretion will endanger their employment and steer towards a restrictive and conservative application of regulations. This is why we have established bodies such as the Administrative Appeals Tribunal and various Ombudsmen, to independently question bureaucratic decisions.
When it comes to questions of censorship, bureaucratic inertia is even more problematic, as whether a particular piece of content meets the rules is often subjective and arguable. This was highlighted in the 4 Corners program with the example of the anti-abortion Web sites that were blocked due to images of foetuses. There is no logical explanation for this result, expect that a bureaucrat was conservatively applying rules in a subjective manner. This example and the general nature of bureaucratic operation means that freedom of political and general speech is endangered by the filter, to a degree where the benefits of the Filter, which are very few indeed, are outweighed by the need for freedom of speech in a democratic society.