Last week more changes were announced to TSA security screening processes.
From June 30, passengers travelling to the United States will face increased screening of powdered substances in carry-on bags. This will apply to volumes of more than 350ml — about the size of a can of fizzy drink. They're not banned entirely, but you'll need to remove them from your bag as you would your liquids. Examples given include cosmetics, ground coffee or other food items.
Personally, I don't think I've ever carried powder in my luggage for fear of becoming the next Schapelle Corby. But the rule will of course affect anyone travelling with hand-luggage only, or parents with powdered formula in their bags. Jacinda and Clarke, please take note.