Ubisoft has reversed course on the Far Cry 4 keys that were revoked due to alleged fraud. Though these keys were revoked, they now tell GameInformer they are reinstating keys that were successfully activated, though they are working to prevent a reoccurrence, and will continue to deactivate keys obtained fraudulently. Here's word on the keys they are reactivating:

After further investigation into the matter of keys that were fraudulently purchased on EA's Origin store, we are reinstating keys for consumers who already had successfully activated and started playing the games. Any remaining fraudulently obtained and resold keys have been deactivated.