The problem is, forcing restrictions on a password actually reduces the search space, making the password file as a whole easier to crack. It's far better to in

The problem is, forcing restrictions on a password actually reduces the search space, making the password file as a whole easier to crack. It's far better to inform the user of the strength of the password and advise to use a stronger password than to enforce it. If I know the password must have a digit and an extra special character, then I can exclude all passwords that don't have these features from the search and significantly reduce the cracking time. If any password is possible, then I basically have to search the entire space. Sure, the single english word passwords will be the first to fall, but if you advise the user their password is weak, that is a risk the user has taken on knowingly.