Razib points me to a YouTube clip of a 18 y.o. girl promoting scientism over religious superstition. It seems like just a boring reminder of how cool you think you are at that age, as if it took balls to rail against organized religion -- a real iconoclast these days has bigger fish to fry. However, on watching several more of AngryLittleGirl's clips, my bullshit detector went screaming. If I had to bet, I'd say this is another lonelygirl15 hoax designed to appeal to geeky male loners aged 25 to 55. Her hook is blabbing about her atheism and civil libertarianism, so the target audience is the type who you'd expect to be a permanent student activist or work at an independent / used bookstore . I'll review some suspicious features from several of her earliest clips -- when any giveaways are unlikely to have been anticipated or caught due to the inexperience of her and her crew in passing off fiction as reality .
For one thing, the content and form are so caricatured that it sounds like a hack's script of a smart but bratty teenager. I know plenty of those, and though they are annoying, this girl does appear to be very exaggerated. Furthermore, she typically talks for minutes on end without the awkward pauses, "ums," "ahs," "y'know," "the thing is," and so on, that anyone who isn't a professional actor or public speaker would have used repeatedly.
In A Rant Goes Wrong, she says that others have doubted whether she's real, since she tends to look off-camera (perhaps to read the script, get direction, etc.). Her lame response is that she's looking into the flip-out part of her video recorder, admiring how sexy she is. Bitch please. For an example of her repeatedly looking off-camera, see My Religious Background, where it does appear that she keeps looking to her left, and that her eyes make "I'm reading text" movements. In Now You Know, she makes up a statistic (that 95% of Americans are scientifically illiterate) and then chastises the viewer at length if they believed her, making liberal use of the word "gullible." That's exactly what someone is if they don't at least raise their eyebrows when watching her clips. Perhaps this is intended as an irony by her writers.
Another red flag is how the Back to the Future poster in her room is placed, and she is positioned, so that it's almost always entirely visible. It's announcing itself too loudly, again to get the attention of the nerd and geek audience -- "Wow, she likes Back to the Future too!" It's as subtle as a gun over the mantle in a Chekhov play. In general, the shooting and editing of the early clips are too professional to be the product of a high school senior. While the editing techniques aren't mind-blowing, they are noticeably the result of someone who's been to film school or had sufficient training. Since this may not be obvious, just compare such clips to any of those from a typical 18 y.o., or indeed of anyone without professional training. There is usually no editing at all, and if there is, it is very choppy rather than seamless. This is especially true in "confessional" clips, where the person usually just talks to the camera in an unbroken recording. It requires plenty of deliberate effort to break up her confessionals with gimmicky edits.
As an example, see The International Square Earth Society -- there are far too many edits for a high schooler to have bothered with, let alone achieve the level of at least a film school graduate. Evolution Revealed is another heavily edited and stylized clip. She's supposedly taking 4 or 5 AP classes, volunteers, etc., and yet has sufficient time to take on large film editing projects? C'mon! Now, in later clips, judging from the titles, she tries to prove that she isn't fake. I'm not going to waste any more time watching those as well, since the evidence from her early clips is overwhelming.
The internet, and YouTube in particular, have made possible a new trope: a naturally occurring Galatea. That is, it was always possible through literature, sculpture, film, and so on, for loners to create their image of the perfect woman, but it's hard to get past the awareness that she is a figment of the creator's imagination. YouTube confessionals are presumably only made by real-life people, so that a person can anticipate what qualities a loner would endow his perfect woman with and hire a convincing actress to play that part. Thus, those watching her videos get the satisfaction of spying on and being talked to by their dream girl, safe in their belief that she isn't a fiction. The trouble is that someone will always be willing to throw open the curtains and show that the whole thing was a hoax, leaving them adrift in disappointment. That happened with lonelygirl15, and it will happen with AngryLittleGirl as well.
 She's like a somewhat less ugly version of real-life Jacqueline Passey. Interestingly, the actress playing AngryLittleGirl is convincing due to her higher level of biological masculinity. She has a fairly masculine jaw-line for an 18 y.o. girl, and just watch An American Girl, where she makes her hands visible throughout. If you pause this clip at 4:27, you can see that on her right hand her ring finger is noticeably longer than her index finger. This is a masculine digit ratio. It would require a female that far into the right tail of the testosterone distribution to acquire an interest in male geek topics.
 There are, though, three major improvements since the lonelygirl15 hoax: 1) the lighting is more typical of someone's room, rather than professional; 2) there are no passing references to the supernatural; and 3) they hired a girl who is only semi-cute rather than breathtakingly beautiful.
Addendum: I already mentioned the "gullible" motif from "Now You Know," but I didn't mention that in that clip she says that if you're gullible enough to swallow any old factoid uncritically, then you're also gullible enough to be brainwashed by religion. Maybe that's the point of her persona: to show that atheists, who pride themselves on questioning everything, will eagerly eat up a fiction, no matter how egregiously affected her mannerisms, as long as it makes them feel good inside -- in this case, from the belief or faith that a girl like her exists somewhere out there and might even date them.
Whether or not her writers are that clever, there is another obvious instance of beating the atheists with their own stick: namely, that mass media outlets like YouTube are the opiate of the atheist male masses, lulling them into inaction as they give up on real-life girls, preferring daily fixes of AngryLittleGirl instead. In this respect, she far exceeds lonelygirl15 as voyeuristic geek porn.