I am also against the idea of like and dislike button.If you like someone's post simply thank him by quoting his post.Like and dislike button will begin unnecessary competition between users to get more likes to their posts.
It may also encourage buying or selling likes like fb likes are sold.
There is no particular point into quoting someone when you like his post, while you have nothing to say that is pointed at when he or the OP stated.
Other than that, it is indeed a bad thing to allow people to like or dislike posts. In the same way that polls here are useless, that directly goes up for likes and dislikes as well.
I probably don't have to point anyone at the massive armies of farmed accounts. If people like a certain post in the way that it is helpful, then you can tip that person if you feel generous.