Just came here to say that my Steam account (created in the year 2003) has just recently been hacked. Valve notified me of hacking attempts coming from Romania that were successful in gaining access to my Steam account.
I am extremely diligent with account security and typically rotate ~25 passwords over the years. According to my spreadsheet there were only two accounts using the compromised password:
Recommend changing your yahoo password and any other accounts that used the same password.