Great topic!
* what other information style communities are there and what characterises them? The primary information style community is a hobby-based forum with a certain dedicated topic. For example, this forum is for people interested in F1. There are countless forums dedicated to pretty much any sport you can think of, and almost any interest you can think of: stamp collecting, fishing, fitness, etc.
One of the oldest means of communication online is the newsgroup (usenet) from years and years ago. Newsgroups are still going strong and are a fantastic source of information.
* how do communities develop? The best forums tend to be associated with popular sites. For example, people come to this forum looking for GP4 addons, and they find the forum and occasionally run away screaming. Stand-alone forums never seem to be quite as popular unless they are the only source of knowledge available (check out howardforums.com for ANYTHING phone related, as an example). Pitpass.com has a thriving forum community simply because it's an extension of the site and almost acts as a rumours section of the website, as well as a discussion. People enjoy discussing their interests because it gives them a great chance to (primarily) show off their knowledge and assert themselves over others.
* how can a new community be established? See above: tying a "community" to a major "thing". For example, Google Earth has a really really great BBS because the users are all posting little placemarks from around the world, and helping each other out. HL2 has a major forum because there are so many people looking for help, advice, or just wanting to talk about the game. If the biggest sport in the world became chess tomorrow, I'd start up a chess news site and have a forum.
* how can accuracy of the information in a community be assured?"Because there's no quality filter on the internet, you have to rely entirely reliable sources for information, such as major news sites (e.g. BBC, Reuters, AP, etc). Accuracy of ANY information on the internet is very hard to be assured of unless backed up with a link to the something very close to what the event is about. If someone posted a thread here with Alain Prost coming back to F1 racing, this person would be laughed at unless there was a good story reported over at the major news sites for F1.
The only way to have accurate information online is to show sources, as with most things.