I've been in a few for various reasons. There's one where they choose a few redditors at random and you get 7 days to talk amongst yourselves, after that you are banned from the sub forever. That was amusing. Kinda gutting when you get the ban notification.
now that i don't have a reddit account, i guess i can tell you guys about secret communities
someone on reddit made some secret subreddits for certain acievements:...