The karma system is susceptible to abuse and this is evident by remembering what happened to Chuck Norris. It is possible for members to create multiple accounts on old forum and the same will happen here, too. Furthermore, whenever someone criticizes a doctor, they are prone to being creditability-gang-raped by the patients of that doctor. There has also been instances where patients in a guesthouse have ganged up on a member of the forum after a disagreement.
So, no, I'm 100% against it.
I do, however, believe a system should be in place as it would encourage people to post comprehensive updates. Perhaps people could "like" comments as they do on Facebook. On the profile of a user, it should have something that indicates how many "likes" they have per post.
Example: "Frank Garrett has: 231 likes in 184 posts"