The Yen Is on a Tear. U.S. Investors Need to Keep It in Focus. — Barrons.com
By Martin BaccardaxU.S. stocks face a key risk beyond earnings and the economy over the coming weeks, and it's tied to a big move in currency markets that has some investors puzzled as to how and why it's accelerated in the start of September.Japan's yen, one of the most actively traded currencies…