This would have been the ultimate trump card back in the days when websites tried to prevent people from stealing their JavaScript and images by disabling things like right click and using twiddly bits of obfuscation. View source, eh? There is no source, punk!

Of course, the Link: header hadn't even been proposed yet, and the whole "DOM scripting" movement plus tools like Firebug/Webkit inspector has turned obfuscation of web content into a pointless exercise. So, like the author says, this is just a fun parlor trick.