When did “x is a thing” become, y’know, a thing?

OK, so my head is full of cold but I thought I could wander out into Twitter and ask something that was puzzling me, but it seems I might have asked it at the wrong time or the wrong place.  I got back answers that made me think people didn't understand the question.

So there's a formulation that I've seen on Twitter and blogs that is: "X is a thing now" or "is X a thing? Really?".  I suppose I've internally translated it as meaning "X is a meme now".  Except that the formulation seems to have become a meme itself.  And that's what I was trying to ask – when (where/how etc.) did saying that "X is a thing" which means that X has become a meme,  become a meme?

Also what effect does capitalising "Thing" have?  What's the difference (if any) between "We could make that a thing!" and "We could make that a Thing!"?

PS I'm not just asking the question because I want to know.  I'm also interested in how you *can* answer questions like this. It's not something you can search for easily, nor does it seem to show up on Quora… yet.

Originally posted on Lloyd’s posterous