Camping in the Vallée Blanch is officially prohibited by a local bye-law (arêté prefectorale), but is currently tolerated in the Vallée Blanche. (Summer 2002).
If you look down from the Midi cable car station, it looks like a little village at times!
Because it is only a 20 minute walk down from the cable car station, it is possible to carry enormous quantities of gear down onto the glacier, and make yourself very comfortable.
It's a great situation for most Mont Blanc routes, as well as those across the Vallée Blanche (2 hours walk. Shame on you if you take the cable car!!) such as the Tour Ronde, Dent du Géant, Rochefort Arête, Grandes Jorasses, etc, etc.
According to a sign I saw posted on Aiguille du Midi, at the exit to the "haute montagne" area, persons can set up tents pretty much any place they choose on the mountain, free of charge, provided the tents are up after sunset and down before sunrise. During the week of 10-13 September, 2002, I noted a number of tents up at "high noon," in the Col du Midi (3,532 meters). No one seemed to care and I certainly did not see anyone out there performing official duties, fining campers, or ordering them to depart the area.