It's unknown exactly how many people were affected.

If you have an Amazon account, there's a chance you received an email from the company this morning informing you that your email address was disclosed publically for the world to see due to a "technical error" the company experienced.
The email itself is pretty short and reads in its entirety as follows:
Hello,
We're contacting you to let you know that our website inadvertently disclosed your email address due to a technical error. The issue has been fixed. This is not a result of anything you have done, and there is no need for you to change your password or take any other action.
Full story from the WindowsCentral blog...