Official Gmail Blog: Choosing a smart password
Creating a new password is often one of the first recommendations you hear when trouble occurs. Even a great password can't keep you from being scammed, but setting one that's memorable for you and that's hard for others to guess is a smart security practice since weak passwords can be easily guessed. Below are a few common problems we've seen in the past and suggestions for making your passwords stronger.
... because of this: http://mashable.com/2009/10/06/gmail-accounts-exposed/
and this: http://mashable.com/2009/10/05/hotmail-accounts-exposed/
i recommend using 1Password to store passwords btw:
http://agilewebsolutions.com/products/1Password