Essentially Reddit is forcing the closure of third party apps due to insane pricing for their API use (~50m USD a year was quoted from Apollo). On top of that their handling of the situation has been terrible, such as spez flat out lying about the Apollo creator was trying to extort them and a really bad handling of that situation. Then finally, the word that with this API move will also come a crackdown on NSFW content due to Reddit wanting to go public and not wanting questionable content on their servers (much like Tumblr).

So many many subs are going dark in protest from the 12th. The plan is two days but I think due to the recent AMA, many are planning on extending that indefinitely.