https://www.deepdotweb.com/2016/01/23/bitcoin-playing-an-increased-role-in-crime-europol-says/Would you believe that the existence of bitcoin has increased the number of criminality in some countries in the world. This is the issue that was being thrown by the EuroPol and the UK Metropolitan Police. According to them bitcoin has played a huge role on the increasing criminality in their area. They added that a huge number of cybercriminals were using bitcoins in their activities.
This just shows that as bitcoin develops both advantages and disadvantages will tag along.
Yes it is because it is not traceable and all illegal can be made easily to all country. They can use bitcoin because it is very secured money.