While in a meeting today with Microsoft, the Microsoft guy pointed me to a website called Have I Been Pwded. On this site you can enter your email address and it will tell you if there’s any activity regarding your email addy and known hacks. The site is hosted by Troy Hunt who is a regional director at Microsoft so don’t be afraid to query the site, you may be surprised and/or horrified at what you find!
I went so far as to enter a few old passwords I no longer use and found that 1 out of 3 of them has been used by someone other than me. You can also look up known websites that have been hacked.