You point is interesting how speech patterns catch on and become the phrase 'du jour'. I think the internet has changed that dynamic, it used to be only withing people you saw face to face. Now we're exposed to a much wider range of people and styles.

Anyhow, I haven't seen the trend of calling out an entity as being a LARPer. But I have to admit, it's kind of funny. It does make me giggle :)