A government ban is one of such scenarios. If the government makes the possession of Bitcoins a criminal offense, then very few people will be willing to take the risk.
I think that is not the thing that can bitcoin die because now there are some country which bitcoin is already ban but lots of people there are continuous collection bitcoin using vpn.
Yes if the governments will ban it then it will not be a high affect on bitcoin as people will use it only without showing their identity and no one will face any problem from their governmnet because the governments will not know that any one who is using bitcoin is from their country.