Anecdotally I've seen people heavily influenced by what they see on FB. Not so much amongst my professional colleagues who tend to be heavily into Tech, but it's definitely the case among friends and family who aren't into Tech and literally believe every bit of spam that shows up on their News Feed (especially if it aligns with their pre existing biases, although to be fair this may simply be because FB hardly ever surfaces stuff that doesn't align with your preexisting biases.