“More often than not, what people put up online using social media is widely accessible because most systems are designed such that sharing with broader or more public audiences is the default. Many popular systems require users to take active steps to limit the visibility of any particular piece of shared content. This is quite different from physical spaces, where people must make a concerted effort to make content visible to sizable audiences.8 In networked publics, interactions are often public by default, private through effort.”