My normal example is when explaining that something is doable, but very, very rare. Say, for example, your chasing a royal straight flush. They are possible, they do show up, but they are very, very rare. In these circumstances you are definitely "Camping Raster" (be happy if you don't get that reference!).
Still, why does it come into play so easily? The wife and I will talk about "Grinding" out certain family functions or spawn-camping the 2 year old so she doesn't get into something she shouldn't. Okay, we're weird - but if you didn't know that you wouldn't have read this far. *grins*
I wonder if its not unlike reading books, watching movies, etc. and picking up on things that click and moving them on. "I'll be back", "Do you feel lucky?" all evoke similar responses - assuming you've seen or been around people who use the sayings so you can pick them up in context. Perhaps gaming is entertainment.
Either that or we're all just pulling one huge "Jilad at Tenagra".
(Curious about that last one? Look here.)