Some countries are afraid of bitcoin because it will cause some illegal actions such as laundering black money, purchase of drugs and weapons, illegal money transference to foreign countries. Beside that the government will lose taxes from bitcoin transactions because bitcoin is decentralized and is not controlled by financial offices of government.
Yeah these are some reason why in few countries bitcoin is not supported. I think most popular bad activities using bitcoin is purchase drugs. Peoples who doing that feel their identity is safe.
If transactions drug with bitcoin more booming as new criminal methods , truly it will give bad affects as bitcoin image.