NEW YORK/SAN FRANCISCO (Reuters) - Facebook unveiled new ways for businesses to plug their brands, including to mobile users for the first time, allowing them reach its 845 million users directly across all devices as it races toward a multibillion dollar IPO. With new "Premium on Facebook" features, advertisers can even get messages directly onto users' newsfeeds on both computers and mobile devices, giving them a presence on valuable Internet real estate at the risk of alienating users with intrusive ads. ...