"Limit them, earn them, use them to indicate good content" - people are still trying to turn them into a reputation system, and they're a whole 'nother animal. First of all, they are not a judgment of someone's behavior on the board, they're for specific posts. And if you limit them and force people to read a post with certain criteria in mind ("did I like this post better than that last one? Could a better post come along?") you'll suck all the fun out of it and they'll just stop caring at all. And then you'll have all the sig lines like with Reputation, ("if you Liked someone's post please be courteous and Like the post") and it all goes downhill from there.
Why do you want to take such a simply beautiful thing and wrap it in a mile of red tape?