The 2 main forums I run are closed membership ones for several thousand users, therefore I cannot give you links to them to see the function in action.
We came to the conclusion that an 'agree/disagree' option was preferable to like/dislike (as on Facebook etc.) and don't publish the numbers, only the general trend. The purpose is to allow visitors to get a feel of what the majority of members feel about each post and it is the post itself which members are commenting on, not the person who posted. Mods are automatically alerted when a member reaches a preset number of disagree's and is privately warned if it is felt that the member is abusing the system. No such system is perfect and we continue to develop other rating levels.