Amid Vietnam gloom, US company promises riches In this photo taken on Oct. 19, 2012, Australian Brian Tan, right, a "blue diamond" sales executive of Nu Skin, a multilevel marketing company, speaks during a presentation to economic students to expand and recruit distributors for his sales system at Nu Skin's office in Ho Chi Minh City, Vietnam. Nu Skin, which has stormed through Asia over the last two decades, racked up huge profits despite regulatory scrutiny over its marketing practices and the efficacy of the products that it sells. Multilevel marketing businesses have a strained history in China and Vietnam, whose Communist rulers have been wary of pyramid-based sales schemes that have been characterized by some as preying on the dreams of poor citizens. They also fear that unrest as a result of associated scams from the schemes could challenge their legitimacy. (AP Photo/Na Son Nguyen) HO CHI MINH CITY, Vietnam (AP) -- The Australian salesman flashed up a slide of a black Rolls Royce and pitched enticingly to a roomful of Vietnamese students facing an uncertain economic future: join me in selling anti-aging products and the car -- and much more -- could be yours in just a few years. It's a simple formula that has worked well for the company, Nu Skin, which has stormed through Asia over the last two decades, racking up huge profits despite regulatory scrutiny over its marketing practices and the efficacy of the products that it sells. Vietnam is the latest frontier for