This morning, I sent a hoax email to a mailing list I frequent, giving bogus instructions on how to defeat the copy-protection on the new version of the software which is discussed upon the list. I've only received a handful of responses so far, but I've created a page about the joke, containing the original message and the responses (names have been deleted). I'll add to the page as new responses come in.
Some people knew what day it was, but others did not.