> I consider stackoverflow one of the best sites of the whole internet, together with wikipedia and a few others.
Though that has more to do with their community & content than their structure. Of course, SO's structure is part of the reason for its community/content (though I personally believe Atwood & Spolsky's star status was more important), but just copying that isn't going to get a similar site a lot of users or quality content.
Sure, when I say stackoverflow I don't just refer to the technology, but the community, how the site is handled by the founders, the original aims that resulted in the site, and so forth.
Though that has more to do with their community & content than their structure. Of course, SO's structure is part of the reason for its community/content (though I personally believe Atwood & Spolsky's star status was more important), but just copying that isn't going to get a similar site a lot of users or quality content.