Mark Pesce wrote a brilliant op-ed about censorware for Sunday's Age in Australia. Here's a snip:
Last Thursday, Communications Minister Helen Coonan reversed her opposition to a proposal to filter the internet of obscene and violent content. Liberal backbenchers, led by Tasmanian senator Guy Barnett, who find existing internet filters unsatisfactory, argue that a mandatory national filter is the only way to protect children. It's a noble idea, but there's a problem – it won't work.
Link, and see also this related article from Mark on the same subject: "Understanding Gilmore's Law."