If I were desiging a system to compete with Twitter, I'd implement a one-click Block button. It should be as easy to block someone as it is to follow them. It would make a statement to trolls and users alike. To users it would say that blocking is a common thing, don't think about it too much, and certainly don't be intimidated into not doing it. It must be almost as easy to undo. A command to review the list of recent blocks. Facebook comes closest to this. It is very easy to block an account but not quite this easy. I think they're probably heading there. #