Reflecting a little bit on youtube's policy of not showing thumbs down and dislikes, yesterday I noticed that doing so is like wanting to share its traffic with any other website that wants to provide that service. On such site, one could enter the address of the video wanted to be given a dislike or see how many dislikes it gets, or the address and the youtube name of a commenter to give that comment a thumb down (Of course searching first to find if the address or commenter name already exist would be needed to prevent multiple representations). This can also be applied to similar speech restrictions applied by other websites, like for example Amazon's policy not to allow reviewing a product without rating it.
