This is a kind of thought virus used to promote a business or product:
Companies that want you to pay attention to them come up with some dumb meme and then challenge you to disprove it. It is always something insanely easy to disprove, such as “Name a day of the week that ends in ‘Y’. I bet you can’t! ;)”
And everyone dutifully replies “Monday!” “Friday!” “Wednesday!” “That’s easy!”
When you share or even respond in the combox, the post appears on your friends’ stream. Thus, the business that started the thread winds up plastered all over place, providing them with tons of free and annoying advertising. It’s a kind of promotional thought virus spread by people who don’t realize they’re being used.
So, please, just stop it already.