The Cambridge Analytica scandal appears to have taken a toll on public opinion of Facebook, as a new poll shows that love for the social media site has tanked in recent weeks.The new survey (pdf) of 577 registered voters conducted by Public Policy Polling for the Factual Democracy Project (FDP) took place March 23-25—right after the public learned of the massive data breach.Sixty-seven percent of those surveyed, it should be noted, said they have a Facebook account.Thirty percent of respondents said they have a favorable opinion of Facebook compared to 48 percent who have an unfavorable opinion about it. Twenty-two percent, meanwhile, said they are not sure.That adds up to a net favorability rating of -18—a drop of 19 points since September (pdf) when FDP last polled for that information. At that time, 37 percent said they had a favorable opinion, and 36 percent said their opinion was unfavorable.As for Facebook chief executive Mark Zuckerberg, just 24 percent expressed a favorable opinion about him, while 35 percent had an unfavorable opinion. Forty-one percent said they are not sure.Like Zuckerberg, Facebook COO Sheryl Sandberg had a net favorability rating of -11; ten percent said they have a favorable opinion of her and 21 percent had an unfavorable one. The majority—69 percent—said they are not sure of their opinion of her.The poll also shows that majority—58 percent—had heard about Cambridge Analytica\u0026#039;s unauthorized harvesting of some 50 million Facebook users\u0026#039; data, and an even greater percentage—71 percent—think Zuckerberg should have to appear before Congress to explain how that massive breach was able to occur.Based on what they now know, just 12 percent say they\u0026#039;re going to delete their account, and 36 percent said they\u0026#039;ll use Facebook less.\u0022We are watching a historic moment of reckoning unfold in real time,\u0022 said FDP founder Melissa Ryan. \u0022Americans have been playing close attention to story after story involving Facebook\u0026#039;s failure to protect our elections from foreign interference, and now its failure to protect our personal data.\u0022\u0022The stakes for Mark Zuckerberg\u0026#039;s testimony are clear from the polling data. If he wants to turn things around at Facebook, it will start in the halls of Congress,\u0022 Ryan said.\u0026nbsp;Zuckerberg has been facing calls to testify before Congress, and, according to media reports this week, is expected to do so.