Yes, nowadays its being used in crime, they buy and sell online and pay by bitcoin. Because its untraceable. So police cant get clue to caught them. I think its dangerous.
They use bitcoin for being untraceable and you hide your identity to anyone. It is truly that they can use bitcoin in crimes. We can't get them caught in jail but only God knows what are they doing so let the karma do for us. We can't protect our bitcoin all the time, they surveillance our money when we are become busy, they will attack us and our money easily.