You may have heard of this "Message to Scientology" thing on YouTube, of a group calling itself "Anonymous" ominously declaring war on the Church. I don't think that's going to amount to anything. The Church of Scientology is way too big and funded to be disturbed by a few hackers. The Slashdot article about it, though, did lead me to finding this comment by someone who was brought up as a Scientology but eventually left the Church when it excommunicated his mother and he decided to maintain contact with her. (His father and sister have ceased communication with them both now.) Anyway, it's an interesting post with lots of info.
Update (Jan-29): Anonymous hasn't done any real good, but they've already hurt innocent people, getting people to make harassing phone calls to a couple who have nothing to do with Scientology. This is why vigilantism is bad. :\