Karma system? Oh, god, no.
Let's have two examples. Thread in Microsoft forum about Halo 3 being overrated (or Sony forum and Uncharted 2 or Nintendo forum and MKWii if you like).
OP: I don't like "x game", and felt it was overrated.
*Well-developed reasoning*
What are your thoughts?
Reply: FUCK OFF YOU IDIOT, "x game" is the best game ever!
Now, who would get the higher vote? Extreme example, of course, because the replier would be banned. But you get the idea. You'd be voted up if you have a popular opinion.
The only thing that would be good is a "User was warned/banned for this post" and I agree that if there is to be a ratings system, it should be for mods and admins only. Perhaps extending to VGC Gods if all goes well 
(Former) Lead Moderator and (Eternal) VGC Detective 
