Add Authy clarification

docs/security/linode-manager-security-controls.md

@@ -32,14 +32,18 @@ If you enable this optional feature in the Linode Manager, you'll access your Li
 
 ### Select a Token Application
 
-Before you enable two-factor authentication in the Linode Manager, select a token application for your smartphone. We'll use Authy as an example in this guide, but you can use any application that supports the Time-based One-Time Password (TOTP) algorithm. For example, you can use any of the following applications:
+Before you enable two-factor authentication in the Linode Manager, select a token application for your smartphone. This guide will use Authy as an example, but you can use any application that supports the Time-based One-Time Password (TOTP) algorithm. For example, you can use any of the following applications:
 
 * [Authy](https://authy.com/features/setup/) (iOS/Android/Chrome)
 * [Google Authenticator](http://support.google.com/accounts/bin/answer.py?hl=en&answer=1066447) (iOS/Android/BlackBerry)
 * [Duo Mobile](http://guide.duosecurity.com/third-party-accounts) (iOS/Android)
 
 Install one of these applications on your smartphone before continuing.
 
+{{< note >}}
+Authy stores your authentication tokens (hashed for security) on their servers. This makes it possible for them to support backing up and restoring tokens, as well as making it easy to switch devices. However, some users may not be comfortable storing sensitive information in the cloud; for these users, Google Authenticator is a better choice, as the authentication keys are only stored locally.
+{{< /note >}}
+
 ### Enable Two-Factor Authentication
 
 Enable two-factor authentication to start using it with your Linode Manager account.