SAN FRANCISCO (Reuters) - Facebook Inc said on Tuesday it has taken steps to clamp down on "hoaxes" and fake news stories that can spread like wildfire on its 1.35-billion member online social network. The company said it had introduced an option to allow Facebook users to flag a story as "purposefully fake or deceitful news" to reduce the distribution of news stories reported as hoaxes. Facebook said it will not remove fake news stories from its website. Instead, the company's algorithm, which determines how widely user posts are distributed, will take into account hoax reports. "A post with a...