bubba wallace talking to us about his history-making triumph at talladega >> announcer: this is "nbc nightly news" with lester holt good evening the day after that worldwide outage reminded us just how powerful facebook has become, a company whistle-blower described to a senate committee just how dangerous she believes the social network has become the company's former product manager warning that facebook's products harm children, stoke division, weaken our democracy, and much more frances haugen's testimony and the company's own studies form the backbone of the latest effort to rein in the social network. a moment some senators compared to big tobacco's reckoning over the dangers of smoking. facebook, however, pushing back against accusations it places profits above safety hallie jackson has details. >> reporter: facebook under fire tonight >> the company's leadership knows how to make facebook and