Something like SO could work in other fields. But, the devil is in the details of the moderation and incentive schemes. The features of the site matter, but not nearly as much as the community. So, it is more of an anthropology and sociology problem than a build-a-webapp one.
For law and medicine, for instance, you'd have to fight the mindset of "online is not reliable". In programming it is fairly easy to check if someone's answer is trustworthy because you can go and test it yourself relatively quickly and unambiguously. In other fields establishing the credibility of someone answering a question is a lot more tricky. That said, I think bar associations have (bad) sites to ask each other questions.
I agree with Jeff that you can't make a general site of this sort without an intense amount of moderation. (he said so in a recent SO podcast)
In short, it all comes down to the community. And it is probably hard to figure out what incentives and moderation to have for a given community if you are not a part of it yourself.
For law and medicine, for instance, you'd have to fight the mindset of "online is not reliable". In programming it is fairly easy to check if someone's answer is trustworthy because you can go and test it yourself relatively quickly and unambiguously. In other fields establishing the credibility of someone answering a question is a lot more tricky. That said, I think bar associations have (bad) sites to ask each other questions.
I agree with Jeff that you can't make a general site of this sort without an intense amount of moderation. (he said so in a recent SO podcast)
In short, it all comes down to the community. And it is probably hard to figure out what incentives and moderation to have for a given community if you are not a part of it yourself.