Official Google Blog: Advanced sign-in security for your Google account
I highly highly recommend this to anyone who uses a Google account. Yes, it is a minor inconvenience when you first get started, but so many of my friends and family have gotten their email accounts hacked that it is definitely worth it. If you value your Google account and anything that is attached to it – emails, pictures, any online banking or bill paying you may do – please strongly consider turning on two-step authentication for your account.
Official Google Blog: Advanced sign-in security for your Google account.