Google allowed Facebook to import your Google Contacts via an API for years. Last fall it blocked Facebook's access to that API, saying that they'll restore it when Facebook offers reciprocity (i.e. if Facebook begins to allow users to export their FB contacts using a similar API, then Google will reactivate Facebook's access to the Google Contacts API).
Facebook's argument has always been that it doesn't think you have the right to export your friends' contact information (or at least, they're endlessly pondering whether you have that right). Which is a ridiculous argument, because, as has been mentioned elsewhere, they already allow Yahoo Mail users to do exactly that.