I don't think that's a "better argument". I think it's a second, also good, argument that I didn't repeat because it's been mentioned by several other people.

I don't think that's a "better argument". I think it's a second, also good, argument that I didn't repeat because it's been mentioned by several other people. Your argument is about protecting trivial passwords. It's quite common for people to independently come up with the same crappy passwords - the adobe "crossword puzzle" leak was a particularly interesting example of that. My argument is about protecting moderately good passwords. If you use, for example, PBKDF2 with a fixed salt and have a million users, an attacker can try close to a million times as many passwords vs random salts. You can still prioritize cracking with salted passwords in many cases. Say you had a dump of hashes form hackernews, and they were bcrypted with random salts. You'd go after the admin accounts first, then the well known accounts with a lot of influence, then everybody else.