Bitcoin's anonymity is really a great characteristic. It enables users to use BTC in any transactions with nearly no traces. But is this really a good thing? Let us consider utilizing bitcoin in a negative way. Since bitcoin is considered currency, there is no doubt that a person that needs money will not reject bitcoin even if it involves unethical or illegal act.
Due to the anonymity of bitcoin, some uses bitcoin in a negative way [citation needed]. They can easily use bitcoin in paying others to commit crimes. They can even use bitcoin in bribery and/or money laundering. This characteristic of bitcoin are abused [citation needed] and it will never end well.
For the case of terrorism, terrorist can easily purchase weaponry from other country. With the use of transaction using bitcoin, authorities will have a hard time tracing that transaction thus, will give advantage to the side of terrorists.
This is not an impossible scenario. People can now use bitcoin in any way they want to. It's inevitable.
You have to choose. You want privacy, or you want the government to have full access to everything while trusting they will do a good job with the data?
That is the ultimate dilemma. Some people trust governments and think their corruption is small compared to the damage they can prevent from happening, some thing terrorists having access to anonymous technology is not a problem compared to what governments do behind closed doors.
Who is right? who knows.