The diffuser you linked to is an ultrasonic diffuser. All ultrasonic diffusers use water. Other types of diffusers include nebulizing diffusers (don't use water), candle warmers (already mentioned in another comment), reed diffusers (passive diffusing), and Aroma Stone .

MLM are predatory companies where "representatives" sign people up below low them and those new reps sign up more reps below them. Like a pyramid ;) . The more your "downline" sells, the more you make. Rarely do people make any money from these schemes and the products that they sell are always more expensive then what you can purchase from a traditional retailer. They are definitely catching on in Europe and other places but most of these companies are based in Utah USA.