Really?, in the eleven years since the original writeup, and mostly in the past two years or so, has become an interesting expression of slightly mutated meaning, deviating somewhat from its original use.

Let me explain:

Sometimes prefaced by "Wow!" (as in "Wow, REALLY?!") Really? is now often used to respond to something quite rude and/or weird that somebody in close proximity to you has done or said. Most of the time it's something done and/or said to you or a person that you're with. The biggest difference with this usage from the original has a lot to do with how it's said that's difficult to explain in text. It's all about the inflection. I guess the best way I can describe it a really-annoyed, I can't believe you just did/said that, tone of voice.

It seems to me that it has become useful in situations where you would like to tell Mr. or Mrs. Rude-Ass off for the drive-by (or walk-by) ruding, but do not wish to engage in a major confrontation. This could be for various reasons, like you're pressed for time, or have a propensity for pissing yourself in intense social situations.

So Really? has really become a sort of way for you to express a certain level of mild condemnation for the infraction, to let the person know that they have behaved in an unacceptable manner, but without tossing an insult or judgment, which leaves the other person free to just ignore you, or give you a dirty look, and go on about his or her business. Because if you really yell at the other person, or insult them, or pose an argument, then you're really starting something the other person will feel compelled to finish.

However, after, say, somebody buts in front of you while you're in line to order a Lardburger, if you just say "Really?!" (and perhaps add a scoff), you might get a mad-face from the other person, but he or she will likely not engage you.

Also implied in this short response - and this speaks to the literal meaning of the word a little - is a sense that you thought they did wrong, but there's a slight possibility that you are actually the one who is wrong and perhaps making a big deal out of nothing. It's like summing up "Did you really just have to do that? That was rude! I might be making too big a deal out of this, but come on!"

However your response is taken, again, the other person probably will not start a confrontation.

But, if he or she says "Yes, REALLY!" then, well, it's ON! (like Donkey Kong)