First of all, why does it seem like I can never reply after a couple levels of the threading?
Now, on to the actual reply...
The difference between the mafia and the government is that the people have a say in how the government operates. If the mafia doesn't think you paid your dues, they break your legs. If the government doesn't, you get a trial. If mafia dues are too high, that's your problem. If taxes are too high, elect fiscal conservatives to get the taxes lowered. If the mafia don thinks you insulted him somehow, he can summarily kill you. If you talk shit about Obama all day long, the government can do nothing.
Moreover, what about foreign governments? Forget the local stuff... if we have no government and no army, what prevents Canada from taking over and becoming your ruler without even giving you the benefit of Democracy?
I'm going to guess you'll say civilian army, but without government funding, training, leadership... well, they'd get creamed.