The fact of information being available does not make it known. Billions of people have never read The Woman in White by Wilkie Collins, despite it being freely available in most places around the world, for example. The use of spoilers is not to protect the copyright of the writers, but to protect the surprise of the readers when they discover what has been written.
This is our monthly thread for collecting these little gems and pearls of wisdom, rationality-related quotes you've seen recently, or had stored in your quotesfile for ages, and which might be handy to link to in one of our discussions.