Control your personal information
It's not just celebrities who are vulnerable to such password-recovery attacks-- everyone is. If you're a US resident and you haven't locked your credit reports with the major consumer credit reporting agencies, you're vulnerable too. Anyone can get a copy of your credit report in the US by claiming to be a potential creditor or potential employer and paying the appropriate fee.
If you don't supply real personal information as answers to security questions, that information can't be leaked by the possessor (Yahoo) or used by an attacker.
Security questions present an especially severe vulnerability because they are not optional on most systems.


