Hosted chats on Twitter where anyone can participate and a panel of experts offer advice. This opens up the community to anyone who might be interested and allows knowledge of be disseminated to a wide network quickly.
These types of chats have popped up in the education realm, where anyone who's interested can tune in to a hashtag at a particular time. The chats are Q&As hosted by an expert panel, who can then offer advice to people tweeting in using the hashtag.
This type of forum means no extra hurdles are in place for anyone to join. It also means knowledge can be easily retweeted out and disseminated into the wild.