When running vipw, you can edit /etc/passwd, but you do not get prompted 
to edit /etc/shadow, nor do the entries get propogated. This means that 
the passwd and shadow files may contain different information, which is 
potentially a security bug.

If you run vipw in Solaris, and change /etc/passwd, you are prompted that 
you should probably change /etc/shadow, "would you like to change shadow 
aswell".

This has probably been a bug since shadow passwords started being used 
in Linux.

I know that people should be using "useradd", or some such, but vipw is 
the BSD way of adding users, and people used to using BSD typically use 
that tool to create/delete/modify users.