As noted, the plug-in Boss mentioned only would allow positive feedback. And no one ever had their opinion influenced by a reputation rating before, so I don't see why it would start now.
What it would accomplish is giving the community the ability to once again identify quality (the lack of which has been the main complaint I've heard from many long-time board members, a fair number of whom no longer post here for that very reason) and set some standards. The ability to "like" a post plays an important role in online communities. It allows the group as a whole to steer the conversation a bit and encourages people after they've made good/well-considered/creative/interesting/amusing posts. The board needs more good stuff and less skull-pounding inanity.