I've worked with two types of businesses when it comes to crisis communication in today's world.
The first group have a plan and are ready to act immediately when something goes wrong. This is vital because people make up their mind quickly as to whether you are a victim or a villian. This group come out with minimal damage because they were able to communicate straight away when people were still forming their opinions.
The second group suffer badly because they were nowhere to be seen in this opinion-forming stage. You need PR help, but it can take time for that to arrive. You must be ready to act yourself and have a plan in place for that.