Facebook is a place where people share everything or anything they feel like sharing and only their friends and friends of friends see it. Actually I have control over my Facebook Privacy settings.. I can control who sees my stuff.
SEOmoz is all web related/marketing and I have no control over who sees my posts.
You are correct, Facebook does not have a dislike button. However, SEOmoz does. If someone is going to give a thumbs down for something, how am I supposed to know what his/her thoughts where? How am I supposed to learn from my mistake or how are they supposed to learn that I am right.