This problem isn't really new for some parents of today. But the thing is, there's always a reason why teens get involved in such inapproriate activities, mainly because they think no one cares or understands them. The bad company and the vices they have seems to be the only avenue for them to express themselves and become a part of something that understands them.
It's difficult to be dealing with out of control teens but there are different options that parents may consider. You have the choice to look at your current situation and do everything in your power to make it better. Know what is going on in your teen's life. The defiance you are seeing could be a result of an underlying issue that they don't know how to deal with and have been unwilling to talk about. If you can get them to talk, and lend an understand ear you may make great headway in their behavior. Therefore, knowing and understanding what is going on in your child's everyday world is very important. If all else fails despite your efforts to reach out, then it might be high time to consider counselling or tough love boot camps.. Serious teen problems may just need serious professional help. Your teen might hate you for it, but then again, it's more important to be offering them all possible solutions than just give up on the situation and wait for them to either hurt others or themselves more.