Hi,
No I have not built it to allow all authenticated users to have a blog. The blog is desinged for use by "trusted" users. Users are able to put in javascript widgets for good or bad purpopses using the blog. Letting just anyone have a blog means you will end up with cross site scripting attackes entered by some users. You can create a blog for any user that you trust but there is no automatic provisioning of blogs. You would have to build a custom feature to do that.
The forum module allows multiple forums just as you see on our forums page there are different forums for different categories of topics. We don't have nested groups but you could put multiple instances of the forum module on the page, so one module can be for Developing Languages and then you would add a forum for each language. Then another forums module instance can be added for other topics.
Hope it helps,
Joe