In reply to mockerkin:
Yes, you are more vulnerable to frostbite in the same area if you have received cold injury there before. There's been a fair amount of research in this area which supports this.
Nerve damage can obviously also occur.
News isn't all bad though. Prevention is key. All the common sense stuff like keeping hydrated, well fed, core warm and your hands warm and dry without anything constrictive (rings etc). Another option is vbl gloves.
Some people swear by Vapour Barrier clothing. There's a small american company called RBH designs who have a good reputation here. Some people with Reynaud's syndrome swear by their vbl gloves and mitts. Lots of polar and high altitude stuff been done with this kit.
hope that helps
Jon