Guam is preparing for its largest military build up since World War II.The U.S. territory is expecting an increase of 8,000 marines by 2014,as personnel and their families are transferred from the Okinawa base in Japan. The massiveexpansion is expected to cause an economic boom in Guam, providing jobsto around 30,000 of the island's unemployed, but concerns about drasticpopulation increase and weak infrastructure worry some.