Impersonating celebrities on social media. Not in a celeb rp way, where they make it clear that it's roleplay, but making Twitter/Instagram/whatever accounts and pretending to be that person. It's even more embarrassing how many people will fall for it no matter how inept the impostor is, like the person I saw pretending to be Daisy Ridley on Twitter... who linked to her Instagram... to a post where she says she doesn't have a Twitter.