Remember last year's well-publicized leak, which exposed some celebrities' nude photos? The story not only made some individuals' day (and probably night), it turned to be a very educating precedent. For instance, it made many people realize that their pet's name is not the safest password, and two-factor authentication is not meant exclusively for IT geeks, but for any Swarovski-adorned iPhone owner as well. However, 2FA in iCloud, as well as in Gmail, Facebook and many other web services, is optional. Thus the consequences can be devastating, especially if your work at an Internet company. Here's part 2:
ID on a smartphone
If you are a frequent traveler, a smarter way to enable 2FA would be a special app. Unlike SMS, this method of authentication functions offline. A one-time password is generated not on a server but on the smartphone (however, initial setup will require Internet connection).
There are a number of authentication apps, but Google Authenticator can definitely serve an industry standard. Besides Gmail, this program supports other services like Facebook, Tumblr, Dropbox, vk.com, WordPress and more.
Should you prefer a feature-pack app, try Twilio Authy. It's similar to Google Authenticator but has a couple of useful options.
First, it allows you to store certificates in the cloud and copy them to other devices (smartphones, PCs, tablets and many other platforms, including Apple Watch). Even in case of your devices being stolen, you still have control over your account. The app requires a PIN every time it's launched, and the key could be revoked if your device is compromised.
Second, Twilio Authy makes your life easier when you start using a new device, unlike Google Authenticator.