that's a great topic!
I believe the most important reason to the downfall of the Mafia is that the Dons started to earn so many power that the main authorities started to really worry about them, and then the law almost finished the mob.
well pacino priness, I don't think it sounds so stupid, because the Mafia Dons were all respectful with the civilians. today we have robbers that kill anyone for no reason, while the mobsters just killed other mobsters or someone who messed with them. I'm not saying this is right, but between these two kinds of "bad guys", I'd rather the mobsters.