Also, if you're trying to bruteforce just any hash from a long list of hashes, an unsalted hash means that you can try every word in your dictionary against all

Also, if you're trying to bruteforce just any hash from a long list of hashes, an unsalted hash means that you can try every word in your dictionary against all hashes at once; for Facebook's 500 million users, a sufficiently-long salts (bcrypt's 64-bit salt qualifies) really does help a lot.