There is so much in that one little mark—that squiggle-dot.
It indicates that information is missing. How much is left up to context. It could be that someone is looking for an affirmation that they are supposed to be keeping the pigs in the pen, or banking the airplane one way or another. It could be that someone is missing one part of the equation, or that they know nothing at all.
The most fascinating thing I’ve noticed recently, however, is that it can stand on its own. My generation is using it as a sort of shorthand, and in very different contexts: 1) the asker doesn’t know where to begin asking questions, or knows that they are starting from nothing, and wants to know everything, or 2) the asker and the answerer both know very well what the question is, and so it’s a waste of time/space to write the entire thing out.
Given the efficiency of typing, I really don’t get that last one, but I’m totally guilty of doing it, anyway. That’s the only explanation I can think of.
I mean, this isn’t entirely new, just using the question mark to express confusion. Cartoons and comics do it all the time, and have for a good long while. It’s just that it being used this way as a sort of colloquialism seems rather new. I don’t know—maybe I haven’t been paying attention enough.
Just my thoughts on this little trend.