Alice, Bob, Carmen, Dave and Eugene are playing Mafia.

Bob and Carmen are Mafia.

Everyone elects the Chair, and Alice gets elected! Alice, being innocent, has no clue who's Mafia. The town lynches Eugene.

Next day rolls around, there's Alice, Bob, Carmen and Dave. Bob and Carmen manage to convince Dave that Alice must be Mafia- she made sure Eugene died!

Alice gets lynched, Bob and Carmen turn slowly to Dave, smirking. Game over.

Now, rerun that scenario again, but put Bob in the Chair. Bob uses his influence to lynch Eugene, but then everyone suspects Bob. They lynch Bob. One DF down, one to go.


_______

Obviously we don't WANT to put a DF in the Chair. However, as Fox points out, there's always a silver lining- whenever the Mafia does something, you can try to figure out what they did, and why. And when you have the "what" and the "why," you can often get the "who."

Basically, townies start the game in a haze of ignorance. Information is the key- and its not always peacefully obtained.