The idea is, more or less, that if a site receives a takedown notice concerning a particular copy of a work, it should then automatically delete all copies of that work and, more importantly, block that work from ever being uploaded again. This may sound good if you're not very knowledgeable about (a) technology and (b) copyright law. But if you understand either, or both, you quickly realize this is a really, really stupid solution that won't work and will have all sorts of dangerous unintended consequences that harm both creativity and the wider internet itself.