Advertisers, agencies and social media combine to tackle online threat

LONDON (Reuters) - Sixteen of the world's biggest advertisers have joined together to push platforms such as Facebook , Twitter and Google's YouTube to do more to tackle dangerous and fake content online.The Global Alliance for Responsible Media will also include media buying agencies from the major ad groups - WPP , IPG , Publicis , Omnicom and Dentsu - as well as the platform owners, the group said on Tuesday at the ad industry's annual gathering in Cannes, France.Luis Di Como, executive..