It's becoming a regular thing, the leak of thousands of passwords from sites that everyone assumed had professional, strong security measures in place. Every time it happens, like it just did at Yahoo, you can laugh at the worst and most popular passwords. But keep in mind that even those with secure passwords are now vulnerable to cross-site attacks if they used that same password elsewhere.
It is, in other words, a great time to brush up on how your passwords are stored online and how to make them stronger.
Statistics about Yahoo leak of 450.000 plain-text accounts [Säkerhetsbloggen]