The Ideation page allows for Liking or Unliking a proposal. From what I've understood, you need a certain number of Likes for BP to consider the proposal to be implemented. Unsure if the threshold is 10 or 15 likes. With the introduction of Unlikes, I assume it is the sum of +Likes and -Unlikes that have to reach the threshold set by BP.
The Unlike button made me wonder as to why it was there - are we trying to mimic a Facebookean popularity contest? I certainly hope not and therefor hope the Unlike button will be removed.
If it does stay however (depending on the number of likes on my proposal :-), I'd prefer to have motivated Unlikes. In other words: If you Unlike an idea, you have to motivate why you don't like it.