Birthdays, anniversaries, childrens' and pets' names - there are millions of "common passwords". Trying them by hand isn't something you'll live ling enough to do. That's why there are computer-driven password crackers. And they only work against weak passwords. Anyone who uses military-strength passwords will be a forgotten memory before they crack one. (And that's what password generators generate - military grade passwords. Try guessing a password that uses a 30 character upper and lower case alpha, punctuation and digit password. In 30 years or less.)