The problem isn't just rainbow tables. Md5 is a fast algorithm. Sha256 isn't much slower than md5. You want anything auth related hashed using a slow algorit

The problem isn't just rainbow tables. Md5 is a fast algorithm. Sha256 isn't much slower than md5. You want anything auth related hashed using a slow algorithm - speed is your enemy. That's why bcrypt and the like are popular, because you can adjust how long it will take to calculate.