Something most people can't understand or handle. Could it be that it is harder to judge what people mean on the Internet with text, or is it that so many people are ignorami?
Friend: "Are you looking forward to the exam tomorrow?"
You: "Yes, sure! I can think of anything more exciting whatsoever!"
Friend: "Yeah me too :)"
You: "You know that was sarcasm, right?!"
Friend: "Sure, I knew that!"
You: "Sure..."