Certainly there is more complexity than spam filters, and cultural differences, subtle nuances which are hard to train a system to auto-classify; things that need to be generalized to new cases that arises- that may be wrongly classified in the beginning, etc. Nevertheless such systems can be built from simple cases to more difficult ones step by step and gradually reduce the demand on humans to perform these tasks. Based on some other comments on this thread, I realize FB is already using these methods mostly in languages with plenty of data, and someone also in this thread has made an interesting comment about using machine translation to apply these systems to other languages. I think this will be less of a problem in the near future. (edited)