To my understanding, the danger is in leaving anything there with personal info (paypal info that could be used to determine banking or credit card info, phone numbers, any of what people call "Sensitive info." If you were already careful, there is not much danger of that falling into the wrong hands. However, there are also the algorithms which can be used to determine search history, interests - the kind of things that could be sold to marketers and advertisers - basically a lot of the same issues with Facebook, except that Russia has also shown itself to be a hostile power willing to try to manipulate Americans to do what they want, and the data is coming back about how trolls working for Russia were able to do that using people's prejudices along with the way Facebook organizes and delivers its information. If the Burner community didn't meet and organize on FB, I'd delete it too.