Anonymous communities and memes
Anonymity is worn in layers on the internet. Many fans will have a user name or handle online unrelated to their real name and identity. There are many reasons fans do this - simply a desire to separate their hobby from their real life, shame or embarrassment over their fannish pursuits, concerns over the ramifications in real life of being assoicated with sexually explicit material, or just to experience the freedom of exploring another persona.
Of course once online a username becomes an alternate identity, and there may be occasions when a fan wishes to engage in activities they don't wish to be associated with. Some fans create sockpuppets - accounts under other names, and now communities operate to allow fans to post anonymously - with no username at all.
Abbreviations used in Anonymous communities
Anonymous posting poses its own challenge and so a system of abbreviations has arisen so that people have an idea of who is speaking:
OP = Original poster AYRT = "I am the anon you're replying to."
DA = "I am a different anon from the one you're replying to."
NA = "I'm a new anon who has not commented on this thread before."
SA = "I'm the same anon, replying to my own comment to edit/elaborate.
Many communities will have their own subset of jargon.
Reddit is an anonymous social media & news site where members ("redditors") create username(s) to submit posts & comment in threads. A "throwaway account" is an account that's used to ensure complete anonymity by creating a username that won't be used again in order to post or comment something particularly revealing or identifiable.
- see SPN Reddit Communities
These communities are the havens of the extremely celebrity obsessed - such as Tinhats. Anonymity is used to protect individuals from disapprobation of other fans. Activities include the discussion of the minutiae of the celebrities lives, theories about their relationships, career speculation and internet stalking.
General anonymous memes
Commonly called "anon memes" these are communities where fans post anonymously on issues that they feel they cannot, or don't wish to discuss under their username be it fellow fans or characters on the show. Some begin as "hate memes" that is a place to insult and be generally cruel to fellow fans, but the conversation usually broadens out to include discussions and arguments on the usual topics of fandom interest. Some fans argue they play an important role in allowing fans to speak out safely against behaviors such as racism, while others argue any good is out-weighed by the personal abuse often targeted at fellow fans.
- see also Secrets communities
These are usually one-off communities, or comment threads on personal journals, where people post compliments to each other.
These are communities which run fanfic challenges, where fans anonymously leave a prompt based around a sexual kink or situation, and other fans write short stories based on them. The prompts often cover topics generally considered taboo. In a fandom where Wincest is widely accepted, obviously everyone's definition of what this is varies widely. Anonymity allows fans to write porn that may involve issues they may not wish to admit to liking, although some fans will later repost the stories under their username.