I saw a post about textfile stenography, maybe linked from here or reddit. It used a source text (the example might've been from textfiles.org or a site like that) to hide messages, which looked like the text with glitches or typos or something. I don't not where it is. Here is something that encodes messages so that they look like spam: http://www.spammimic.com/

Y'know how people control botnets with irc or webposts? Maybe it is something like that, as other have speculated. But them why would they be posting messages lots of times? That's a problem in my ideary.