I think the biggest problems will be created by Government and central banks. Because bitcoin will spread more quicker than today is and that will be a huge headache for politicians thus to the government and banks. And if!! I mean if the government allows bitcoin transactions in future then I think they will put some rules and regulations on bitcoin which will not be user friendly and transaction costs minimizer. So you know what will happen if they do that, it will have multiple effects and that effects won't be good for bitcoin. And they don't want good effects at all.