What about the API? It wouldn't be at all hard to make a "Facebook-exporter" application using that. The question is: why would I bother doing that? Facebook is crap as an address book, it's the other bits that are useful... Whatever other reasons there are to think Facebook sucks I don't think this is one.
What's interesting about this argument, is that facebook used to have a feature to export all your friends to vCards. I asked their VP of Product Marketing recently why they got rid of the feature, and he claimed it was to protect users from spam. "Facebook is all about edge cases, and we haven't had the time to focus on the problems that would cause", or something to that effect.