I was shocked when one of my clients sent me a screen shot showing TWO facebook like buttons on his website - one under the other. I went in circles for a couple minutes trying to see if maybe something was happening twice in JavaScript when I found this article:
http://stackoverflow.com/questions/7343277/like-button-just-started-showing-duplicates-has-something-changed-on-facebooks
Here's what my code looked like:
// append like button fbLike = $('').appendTo(social);
Apparently, this recent FB update conflicts with the class name 'fb-like' ANYWHERE in your DOM. All I had to do was rename my div wrapper from fb-like to fblike and everything was fixed.
How odd is that!