Working with the definition of direct internet censorship as government-related organizations preventing certain things from being passed across the www due to legal, moral, or political objections it is impractical to censor the internet. There are over 11.5 billion web pages, and the web is used by almost two billion people. The sheer scale of it makes it near impossible to check and censor each page to ensure nothing which would be blocked is allowed through. Adding to this problem is the subjectivity and complexity of checking exactly what would fall under material to censor under any sensible legal framework, which prevents automation from reliably picking out sites to censor from innocent ones. The resources required to check each web page (let alone other forms of communication like IRC) for censorable material would be so huge that it would cripple any economy, the alternatives being largely automatic censorship which blocks many legitimate sites (Australia blocked a dentist's website), total control over internet access like North Korea which is severely limiting for the public and businesses, or using a mixture of intimidation and wide ranging blocks which catch legitimate sites as China does.

Some may say the cost is worth it to prevent enemies of whatever country they are living in communicating effectively, or block things they view as immoral, however censorship will never prevent these things. It simply drives them underground where they are harder to track. Public Key encryption software, proxies, data havens, and the TOR network have all become far more popular in repose to what many people see as overly invasive governments censoring directly or by making it common knowledge that anyone found using the internet in certain ways will be punished. The only country with near-perfect internet censorship is North Korea. Their model of all computers with internet access being government controlled is both costly and massively limiting for the population, hardly a good example to follow.

Even discounting practical problems there are serious moral and political issues with internet censorship. The most popular form, blacklisting sites classed as illegal, is very hard to hold governments accountable for since almost by definition the list of sites the state does not want people to visit must be kept secret. This means a government willing to abuse it's position could easily shut down sites for any reason without the public finding out whether it was justified. Internet censorship has in almost all countries using it extensively become a means not just of ensuring security, but also of suppressing freedom of speech, a fundamental human right. Allowing it here will likely lead to similar problems. Even democracies are not immune to using internet censorship as a political tool as Australia has proven with its attempted blocking of wikileaks.

Since it would be impractical to thoroughly censor the internet, would drive groups underground, and attempting to do so makes it far easier for a government to restrict the right to freedom of speech, the problems with direct censorship outweigh the benefits. We should not expand direct censorship.