Just a heads up to all. Read the linked article and verify that Google's 2 step authentication is activated on your account. If you haven't heard about what happened to Mat Honan and want to find out more than read this article.
Two-factor authentication means "something you know" (like a password) and "something you have", which can be an object like a phone. Here's a simple video about how it works:
Please visit the linked source site for more information, myths and recommendations. Do you have two-factor authentication enabled?
Source: www.mattcutts.com/blog