> I see the mantra ‘salt your password hashes!’ > repeated over and over, when its only real > value is against rainbow tables

This is dangerously incomplete reasoning. Salts real value is that if multiple password hashes are Leaked simultaneously then each must be cracked individually. In the Adobe leak password hints were included, which allowed for very easy guessing of passwords, and because there were no salts even if you had no hint if someone else had the same password and an obvious hint you were cracked.