Can you imagine how horrible that would be?
Let's say you say something on here, like say "Oh I don't like the character development of Goku" or something like that, and someone agrees with you. Another agrees with you. Soon, you got 100+ people liking your stupid comment.
Someone doesn't agree with you, so they get up in your face about it. "Yeah well XXX had worse!" and someone agrees with that guy, another doesn't and so on and so on.
It would be complete chaos.
And imagine if posts were sorted through likes/dislikes....oh god.