If not, then add it.
https://developers.facebook.com/docs/reference/plugins/like/
Uhh..
Hate to Reply to a topic 16 days later but I'd say no..
Would say that we should have it considering it'd be a form of advertisement.
If there was a button like that on the forums, it would be easier to advertise via your own facebook profile. If you going to share it tho.
Doesn't matter to me tbh.