I've never seen it done in the Q, but I could see how in BW it would be more commonplace.

I'm a cynic by heart, and while I'd like too think my fellow paddler would respect this practice, but I have no doubt that some people would set-up camp and claim " that" trumps a pack on site. I've seen it happen in car camping parks where people leave coolers/etc and find the site taken anyway :(

I think at the very least, I'd hang my tarp and then leave pack under it.