Laurens,
There are a lot of helicopters, for all sorts of reasons, I guess. While in the Italian portion of the walk they were around all the time; it was hard to get away from the sound of them all day. A lot of what they did was supply the gites and refugios with food and supplies, but I'm sure they were also keeping an eye out on walkers. Later in the evenings they usually disappeared though and I don't think it was much problem to just set up your tent in a secluded spot. The area at the base of the slope on which Refugio Elisabeta sits, a big river basin, is one great spot for setting up your tent, and quite a few people did it. Some of the refugios frowned on wild camping, but at Refugio Elena, since the beds were full, I just asked and they let me camp out back (amidst the cow patties, unfortunately). In most cases I don't think you have anything to worry about. Just be discreet.

