A lot depends on the goal of your website.
If you're seeking to create a sense of community and foster wide ranging discussions, what DoCo has right now is a very good way to go.
If you're looking to establish what's primarily an "Experts Q&A" site (where you go in, get what you need, and get out) then stackoverflow's model is probably better.
If you want to develop a community built expertise"repository" along defined subject lines, then go with a wiki.
But think it through first. Especially if it's an existing community.
FWIW, some years back I participated in a web community that switched from a "flat" forum format like we have here to something very similar to the stackoverflow thing.
What happened was that the discussions eventually began dropping off because 90% of the new membership was coming to the site simply to get free tech support and consulting. And once word got out (wrongly) that it was a "Q&A site" they got a lot
of new people.
Wasn't long before the people with the real expertise
began to resent constantly having their brains picked by folks who acted like it was owed to them. You would not believe the demanding tone some people adopted. One twit (who used the handle pcExpert
) even went so far as to loudly complain about the occasional bits of joking around that went on. The site lost one of it's oldest and most valuable contributors when "pcExpert" flamed him for getting a little too playful with his replies. After that, the guy stopped showing up, and within a few months the rest of the "old guard" also disappeared. The site gradually folded up about a year after.
It's amazing how a simple software or format change can alter the entire social fabric of a web site.
Something to think about anyway.