Recent big sites that closed down: Jezebel, Pitchfork, Vice, Popular Science, and my hopes for the Messenger were dashed when they announced their demise: thehill.com/…/4440773-news-startup-the-messenger-…
That said, there are always new sites, but gaining trust and reputation takes time.
Social sites seem doomed to crest and then fall. Digg? MySpace? Friendster? Who remembers the good old days of (moderated) UseNet? Do we want any of those back? Would any of them have remained were it not for spam/bad-actors?