In reply to dan bulman: A friend and I investigated a new sea cliff a few years ago, we just put in our own stakes... Took them out again when we left but if we hadn't wanted to keep them for other exploration we would have just left them in place.
Really you just need to be responsible - take long stakes, place them sensibly and check they are not going to waggle loose and come out. Can't see any reason that you shouldn't do that yourself.