The social network said that's a tall order, considering over 126 million Americans were exposed to the 80,000 updates and 3,000 ads Russian troll farms posted on Facebook and to the 120,000 they posted on Instagram. Its general counsel argued that he wasn't sure Facebook could even identify everyone who saw those posts, since the company got its numbers from computer models, not from actual counts.

Nevertheless, critics are having a hard time believing the counsel's explanation, since Facebook is known to track people's Likes and clicks for algorithm and ad purposes. Intelligence committee vice chairman Senator Mark Warner likened their request to telling people in a hospital if they've been exposed to a disease. There's even a Change.org petition calling for the company to inform users how they were exposed to Russian propaganda that has garnered over 83,000 signatures as of this writing. Widener University law professor Christopher Robinette told Reuters that the courts likely can't compel Facebook to notify users if they were served Russian-linked ads and fake news, so it will all depend on what the social network decides.