Mutual vs. in common

OK this pisses me off so I'm just going to explain it once.

A mutual friend is when you and another person both like each other. Your friendship is mutual. I would highly recommend that you try and ensure that all of your friendship are like this, otherwise you are a bit weird.

A friend in common is where you and someone else are both friends with the same person. It is the most interesting thing about social networking sites (yes, more interesting then being a pirate zombie, if you can believe that).

Just because Charles Dickens and Facebook both seem to confuse the terms, doesn't mean I have to like it.