LinkedIn Password Leak
In June 2012, hackers stole millions of LinkedIn users' login details, and these appeared on a Russian website.
Supposedly, affected LinkedIn users had their accounts locked and received an email advising them to change their password, so most LinkedIn accounts should be safe now.
However, the wider problem from the LinkedIn leak, or indeed any leak of passwords, which seem to occur too regularly, is that many people use the same password for multiple sites. Thus a hacker who has obtained someone's LinkedIn password, may be able to use it to break into Gmail, iCloud, Hotmail, Ebay, Facebook, Twitter, Amazon, Paypal, or any number of commerce or social-networking sites.
So it's not only important to change a password for an account that has been compromised — for whatever reason — it's important to change any other services you use the same password on.
Even better, don't use the same password across different services at all. If something is hacked, your other accounts will be immune.
It's also worth noting that if your system has been infected by any sort of malware, you should change many of your passwords. It's quite simple for a virus, trojan or any malware to retrieve passwords from your system. Succcessfully removing the virus doesn't mean it didn't “phone home” with some of your information.