I'm guessing a -1 button would be only as attractive to FB as a dislike button.
With a -1 and dislike button comes a visible downside to being present on FB, especially for organizations, the potential to be unpopular in a tangible, measurable, way. Organizations would then think twice about being on FB when before it's might have been a no-brainer. Even if the number of dislikes is not publicly visible, it may be to the owner of whatever it is being unliked, or owners may request for it, and when an owner sees that number, may decide that it's bad to have a FB presence.
Considering the downsides of a -1/dislike button, why would FB want it from a revenue and growth point of view?
With a -1 and dislike button comes a visible downside to being present on FB, especially for organizations, the potential to be unpopular in a tangible, measurable, way. Organizations would then think twice about being on FB when before it's might have been a no-brainer. Even if the number of dislikes is not publicly visible, it may be to the owner of whatever it is being unliked, or owners may request for it, and when an owner sees that number, may decide that it's bad to have a FB presence.
Considering the downsides of a -1/dislike button, why would FB want it from a revenue and growth point of view?