Cory Doctorow has an excellent essay on how the plans of the big media companies to require all web hosting companies to filter the traffic of their customers will hurt everyone.
Viacom and others want hosting companies and online service providers to preemptively evaluate all the material that their users put online, holding it to ensure that it doesn’t infringe copyright before they release it.
This notion is impractical in the extreme, for at least two reasons. First, an exhaustive list of copyrighted works would be unimaginably huge, as every single creative work is copyrighted from the instant that it is created and “fixed in a tangible medium”.
Second, even if such a list did exist, it would be trivial to defeat, simply by introducing small changes to the infringing copies, as spammers do with the text of their messages in order to evade spam filters.
Another example of how relying on electronic barriers usually causes more harm than good.