Bruce I also work at a few forums (as a mod. none atv forums) & it is a nice feature to let peeps know how reputable the person is giving the answer. JMHO
I've seen the feature abused with (-) button too! A green bar gets longer for good rep. and red bar for bad rep. Most of the boards that I'm on have turned the function off! All in all it works! I have seen "threads" for bad and good reviews on people to businesses that work well!