On past forums I belonged to, one word/short sentences were not allowed, and frowned upon. This just caused people to post on every topic just saying they liked it.
I agree one, maybe two people could say they liked the idea, but without proper content it will be hard to follow the thread and sift through all the likes.
I go by the rule of, if one person has said they liked it, then I won't post (unless I had something to give). If I truely liked it, I will send a pm to the thread owner.
I break this in the Visual Curiosities forum as I feel the more encouragement in that area the best.
I still like the idea of a like button.
But of course will agree to anything chosen by those in charge.