I’m not sure about ChinesePod being a “hub” of Chinese learning…as far as it being the industry leader and setting a new standard, no doubt. I would say though that the majority of the Chinese Pod users are there for the podcasts and not much else.
I think you get more of a community learning situation with something like http://www.EnglishBaby.com – which is an English language learning site. The forums and chat rooms there play much more of a central role in terms of learning than they do with ChinesePod.
Although I don’t think that this is because of ChinesePod being poorly organized or anything – it’s just a different set of circumstances for the user base (and also a different age bracket and lifestyle for the users). EFL / ESL is a whole different kettle of fish, you get ESL students coming in committed at a young age, a number of whom hope to emigrate to or at the very least study extensively in an English-speaking country, who economically might not have the means to do so without jumping through quite a number of hoops.
A lot of the students start out with a pretty high competency level in English and live in a media environment which is saturated with spoken and written English. You also have a decent number of EFL teachers dropping in either to grind their own axes, ask for language exchanges, promulgate their religions, pick up women, etc.