I don't know if this idea is useful at all, but in the forums, I think it would be nice to have "like" or "thumbs up" links in the comments section. :)
I'd actually rather not have this, as I don't like it on Facebook, etc., either... it's much nicer to get an actual comment where someone put some effort into writing a response... Unless the dev's need that to see if an idea is popular... but that could lead to other problems of some good ideas getting ignored because they don't have enough "likes".