Is your site targeted towards and/or caters exclusively to that type of service? If so, I'd say just move along now. If not, just remember that DO is a cool company, and will notify you of any warnings it receives. as a US company, you have what we call safe harbor, as long as you follow the law, and remove offending content promptly. If you yourself are the person who posts said offending content, you are except from the safe harbor clause, and will most likely face civil/criminal punishments under US law.

TL;DR: If you don't post them, and are respond promptly to the valid complaints you receive, you should be fine, as long as you don't design your site around just illegal activity, and you don't post the illegal activity yourself.