Follow-up: Facebook has created a truly wrong intuition of data privacy, through being such a closed platform. It's not impossible to create a Chrome extension that crawls your FB feeds and stores that in a database which is viewed as a public website. But people's intuition is that somehow a FB secret group is truly secret and/or forgettable. Snapchat forgettable videos are also creating this wrong intuition. It's, at the end of the day, impossible to digitally forget.