Both attempts were criticised and the US Supreme Court struck down the CDA in June 1997.
There is no settled definition of pornography, either in the United Kingdom itself, or in the multi-national environment of the Internet, where cultural, moral and legal variations all around the world make it difficult to define pornographic content in a way acceptable to all.
I'd not bother preventing a sentiment like the totally hilarious "long necked giraffe" reference. :) It's a shame that all the top answers are existential and defeatist diversions from the programming challenge.
With "cyborg" computational services like Mechanical Turk gaining steam, and almost all software becoming social, it is more important than ever to have a heuristic to red-flag content and bring it to the attention of a moderator!
Please direct any comments or feedback about this document (only! The purpose of this document is to give a general idea of how DALnet, the IRC network on which we all spend so much time, got started and grew to what it is today.