It is always a best practice to use strong passwords.  A major hacking attack last night reset over 3 million weak account passwords to “password” (which is weak and used often). Weak passwords will leave website accounts vulnerable to unauthorized users. 

Hackers group sets weak passwords to “password” for 3 million accounts
http://www.f-secure.com/weblog/archives/00002134.html

QUOTE: Passwords from over 3,000,000 user accounts were apparently set to “password” late last night in a wide-spread hack that affected hundreds of news, retail and Web 2.0 sites. Most affected users are completely unaware of the attack.  According to current statistics, 62% of affected users would not notice such a change as their password was already “password”.

The hacker group named “Obvious” has claimed credit for last evening’s attack. Thousands of hacked Twitter and Facebook accounts posted the message “We are all Obvious! Don’t Expect Us”.  A 1.9 GB file containing more than 3,000,000 user names — and one password — is now available for download as a torrent file via The Pirate Bay.  To avoid problems like this in the future, we are recommending users to change their password everywhere …

Microsoft offers a great online facility to check password strength
https://www.microsoft.com/security/pc-security/password-checker.aspx