It's like you get to start creating this disconcerting notion in people's minds that there's a joke that they're not in on. It's fun to think to think you're messing with the minds of all the normal people that surround you. The other thing that really appeals to me is the fact that there's no punch line or meaning to it. The joke is that there really is no joke. But on the original Web sites that started the trend, the phrase has stopped being such a laughing matter.
Jokes stop being funny when they become catchphrases.