More scams, illegal, fraudulent or spammy messages today come from someone you know. In 2010 spammers started changing their tactics, and we saw a large increase in fraudulent mail sent from Google Accounts. In turn, our security team has developed new ways to keep you safe, and dramatically reduced the amount of these messages. You can help protect your account by using a strong, unique password for your Google Account, upgrading your account to use 2-step verification, and updating the recovery options on your account.”]
Source: https://security.googleblog.com/2013/02/an-update-on-our-war-against-account.html